国外三语习得的研究主要以证明在三语学习方面，双语学习者比单语学习者优势所在。而现阶段国内三语习得研究主要是证明三语习得研究的重要性。在中国有很多蒙古族学生，他们以蒙语为母语，汉语为第二语言来学习第三语言英语。这篇论文试图用定量研究的方法从高考成绩入手研究蒙语和汉语对于蒙古族学生的第三语言英语的学习的影响。 蒙古族学生和汉族学生都参与了此项研究, 并且他们的高考三语成绩被当作有效能力测试。结果表明对于汉族学生和蒙古族学生来说，他们的汉语和英语成绩的相关性都很显著，但汉族学生的汉英成绩相关性要高很多（分别是.688和.354）。通过进一步的研究得知，接下来的分析得知，对于汉族学生和蒙古族学生来说，他们的英语学习能力并无明显区别。为了进一步揭示蒙古族学习者的三语关系，依据他们的高考蒙语成绩，将蒙族学生分成了高中低三个分数档。ANOVA分析显示，三组学生的汉语和英语成绩相关性有些许变化，但依旧很显著。然而，蒙语和英语成绩的相关性随着蒙语成绩的提高而显示了出来。但是，蒙英成绩相关性还是低于汉英相关性。 在研究结果中，稳定的二语和三语成绩的显著相关性一方面可能与汉语和英语之间的语言正迁移有关。另一方面，这个相关性可能也和汉语在英语学习课堂上的高参与度有关。而根据学习者的二语课堂使用情况和语言意识的变化，一语和三语的相关性增长可能源于不同原因。

The studies abroad about third language (L3) acquisition mainly focus on bilinguals’ advantage over monolinguals. While, research on L3 acquisition in China is still in its early stage. In China, there are a large number of Mongolian students, whose first language (L1) is Mongolian, second language (L2) is Chinese, learning English as their L3. This thesis aims to investigate the effect of Mongolian (L1) and Chinese (L2) on Mongolian learners’ English learning by examining the relationship between the three languages. Mongolian-speaking students and Chinese-speaking students from two different high schools are involved in this study and their College Entrance Examination scores in the three languages are used as the criteria of their proficiency in each language. Results shows that Chinese is correlated with English significantly in both the Chinese-speaking and Mongolian-speaking learners but the coefficient of the Chinese students’ correlation between their Chinese and English scores is much higher than that of the Mongolian students’ (at .688 and .354 respectively). Further analysis showed there is no significant difference in English proficiency between Chinese-speaking learners and Mongolian-speaking learners. Mongolian learners are divided into three groups with low-, mid, high-Mongolian proficiency based on their Mongolian Entrance Examination scores. ANOVA analysis shows the three groups also differ significantly in their Chinese and English proficiency. The correlation between Mongolian and English gradually has emerged as the students’ Mongolian proficiency improves though the coefficient is much lower than that between Chinese and English. The stable correlation between L2 and L3 might be caused by, on the one hand, the positive language transfer from Chinese to English. On the other hand, using Chinese as the main medium language in the classroom may also lead to the significant correlation between Chinese and English. The gradually emerged correlation between L1 and L3 may be ascribed to a variety of reasons according to their L2 usage in the class and learners' recognition and analysis.