基于过往研究，Granena和Long（2013a:IX）认为二语学习始学年龄是二语学习最终水平的最大解释变量，能解释其30%左右的方差，其次是语言学能，能解释其大约10%-20%的方差。近些年，随着对学能认识的深入，越来越多的研究探讨年龄效应和学能的关系，将二者结合探讨与语法习得最终水平的关系成为热门话题（如Abrahamsson & Hyltenstam, 2008; DeKeyser等，2010; Granena, 2013a, 2014）。研究者在二语环境和外语环境下，使用不同测试条件（限时和不限时）和不同形式语法测试（如语法判断，元语言知识测试）以及不同学能工具（如MLAT, LLAMA）探讨年龄效应和学能与学习者语法学习成效的关系，但还未达成一致意见。相关实证研究中，年龄效应和关键期效应多被混淆，语法测试和学能测试工具较单一，还未见到使用多种语法测试手段和针对中国学习者所开发的学能工具探讨年龄效应和学能与英语语法学习成效关系的研究。 鉴于以上，本研究探讨始学年龄和语言学能与中国英语学习者语法学习成效的关系。具体研究问题为： （1）不同始学年龄英语学习者语法学习成效存在何种程度的差异？ （2）语言学能对英语学习者的语法学习成效是否有影响？如果有，对不同始学年龄学习者的影响有何不同？ （3）影响中国英语学习者语法学习成效的其他主要因素还有哪些？ 回答以上研究问题，本研究采用方便抽样选取了112名研究对象。所有被试均来自同一省份的17个地级市，且均未参加过任何课外英语辅导班。被试分别完成了英语学习背景问卷、限时和不限时语法判断测试、元语言知识测试和学能测试。 数据分析分别运用了相关分析、描述性统计、单因素方差分析、协方差分析、回归分析、独立样本T检验和配对样本T检验等统计方法。研究发现：（1）英语学习始学年龄与三项语法测试成绩相关不显著，三组学习者在三项语法测试、不同任务刺激以及大部分语法结构平均分上均没有显著差异，但三组学习者的得分趋势大致相同；（2）学能对不限时语法判断测试和元语言知识测试成绩有显著影响，主要体现在3-7岁和8-10岁学习者中，大部分高学能者的表现优于低学能者；（3）语法学习成效是多种因素共同作用的结果，而学能是语法测试成绩最大预测变量，分别解释不限时语法判断测试和元语言知识测试成绩6.5%和9.0%的方差。 本研究的创新点和贡献在于：（1）理论上，本研究为语法学习年龄效应提供了实证依据，弥补了我国大部分研究仅靠思辨讨论探讨英语学习年龄效应的不足；揭示了语法学习成效是多种因素共同作用的结果，始学年龄和语言学能对二语学习成效贡献的论述并不适合我国学习环境；丰富了学能对不同始学年龄学习者学习成效影响的研究，弥补了国内该领域研究的不足。（2）实践上，本研究表明我们不能仅期望过早的学习英语而获得较好的语法学习成效，将国外的理论和研究结果借鉴到我国要考虑我国实际的学习环境；发现测试形式、时间限制和任务刺激会影响学习者的语法表现，这对我国英语语法教学和测试有一定借鉴意义；发现语言学能对不同始学年龄英语学习者语法学习成效的影响不同，这对国内英语教学实践具有重要启发。（3）方法上，本研究采用多项语法测试测量学习者的语法知识，弥补了过往研究多采取单项任务测量学习者语法知识的不足；采用针对中国英语学习者特点开发的汉语版学能工具测量学习者的学能，弥补了国内该领域的不足；使用元分析整合了已有研究，为文献综述提供了方法借鉴。

Based on previous studies, Granena and Long (2013a:IX) argue that while age of onset can account for the greatest proportion of variance (typically around 30%) in ultimate second language attainment, language aptitude is the second strongest predictor variable which typically accounts for 10%-20% of the variance. With a deeper undstanding of language aptitude, more and more studies have been and will be conducted on the relationship between age effects and aptitude. Accordingly, the study on the relationsip between above two factors and the ultimate grammar attainment has become a hot topic in the SLA field (e.g., Abrahamsson & Hyltenstam, 2008; DeKeyser et al., 2010; Granena, 2013a, 2014). In second language context and foreign language context, researchers have used various grammar testing modalities (e.g., grammaticality judgement test, metalinguistic knowledge test) with different testing conditions (timed condition and untimed coindition) and different aptitude tests (e.g., MLAT, LLAMAT) to investigate the relationship between age effects, aptitude and ultimate grammar attainment, and have not reached consensus opinions. In relevant empirical studies, age effect and critical period effect are often confusing, grammar testing modalities and aptitude tests are relatively simple, and few studies use a varity of grammar testing modalities and aptitude test developed for Chinese EFL learners to investigate the relationship between age effects, aptitude and English grammar attainment. In view of the above, this study investigates the relationship between age of onset, language aptitude and English grammar attainment of Chinese EFL learners. The research questions are as follows: (1) To what extent is the difference in English grammar attainment among Chinese EFL learners with different age of onset? (2) Does the language aptitude influence the English grammar attainment of Chinese EFL learners? If yes, is it any diference among learners with different age of onset? (3) What are other main factors affecting English grammar attainment of Chinese EFL learners? In order to answer the research questions, 112 participants were conveniently sampled from 17 different cities in the same province, and none of them participated in any extracurricular English tutoring classes. The participants completed an English learning background questionnaire, timed and untimed grammaticality judgement tests, a meta-linguisitic knowledge test and an aptitude test in different periods. Various statistical analysis methods were used to analyse the data including correlation analysis, descriptive statistics, one-way ANOVA, covariance analysis, regression analysis, independent-samples and paried-samples T test. The results show that: (1) age of onset and scores of three English grammar tests are not significantly correlated, and there is no significant difference on scores of three English grammar tests, different stimuli, and most morphosyntax structures among three groups, but the score trends of three groups are about the same; (2) aptitude has a significant influence on scores of untimed grammaticality judgement test and meta-linguistic knowledge test which mainly appears in participants with 3-7 years old and 8-10 years old, and most learners with higher aptitude have better performance than those with lower aptitude; (3) English grammar attainment is influenced by multiple factors; aptitude is the strongest predictor variable for grammar attainment, which can account for 6.5% of the variane of untimed grammaticality judgement test and 9.0% of the variance of meta-linguistic knowledge test. The contributions of the study include the following: (1) theoratically, this study provides the empirical basis for age effects of English grammar attainment and complements the existing domestic reseach on age effects of English learning which maily rely on speculative discussion; reveals that grammar attainment is the result of a combination of multi-factors, and the statement of impact of age of onset and language aptitude on second language learning is not suitable for Chinese context; enriches the study of the impact of aptitude on second language attainment and complements the deficiency of domestic research in this field. (2) Practically, this study shows that we can not expect to learn English grammar well only relying on learning English earlier, and should consider the actual learning environment when introducing foreign theories and research results to China; shows that the grammar attainment is influenced by different grammar modalities, testing conditions and task timulus, which serves as reference for English grammar teaching and testing; discovers that the impact of language aptitude on grammar attainment is a little different for learners with various ages of onset, which provides guidance for domestic English teaching. (3) Methodologically, this study uses three grammar modalities to measure learners’ grammar attainment, which complements the deficiency of past studies using only a simple task; uses the Chinese version of aptitude test developed according to Chinese learners’ characteristics to measure learners’ apritude, which complements the deficiency of domestic research in this field; synthesizes and analyses the related studies with meta-anaysis, which serves as reference for literature review method.