在英语课堂上，英语教师的指令语在整个教学活动中有着重大作用。有效的指令语不仅能够帮助老师有效组织课堂，还可以促进学生的语言习得。教师指令语的质量与学生对任务的理解和完成密切相关。 在本研究中，作者通过课堂观察和课堂录音对北京一所普通高中英语课堂的教师指令语进行了分析讨论。作者共观察了两名高一英语教师的各三节英语课，并且从中选取了四节课转录成文字材料以供后面的分析讨论。在已有研究和相关理论-言语行为理论和克拉申的可理解性输入的基础上，作者着重分析了指令语的句子结构以及指令语对学生产生的影响。主要发现有：1）从指令语的结构来看，共有六种句子结构：直接指令-第二人称祈使句、第一人称祈使句、省略式指令；间接指令-请求式疑问句、陈述句、陈述句+附加问句。研究表明教师使用的直接指令远远多于间接指令。2）从指令语对学生的影响来看，不同的指令语对学生产生不同的影响。第一人称祈使句和请求式疑问句比较礼貌和委婉，学生易于接受；第二人称祈使句和省略式指令虽然简单清晰，但是第二人称祈使句有时缺乏准确性而省略式指令的过多使用会让学生变得厌烦；陈述句对于学生的英语水平有一定的要求；教师在使用陈述句+附加问句时，一般会局限在几种理解核对语上，不利于充分调动学生的积极性且容易让学生变得敷衍。 根据以上的研究，本文针对高中英语教师如何给出有效指令语也给出了一些建议，希望对高中英语教学能够有一定的帮助。

In the EFL classrooms, English teachers’ instructional directives play a significant role in the whole process of teaching. They are not only important for teachers to organize the class, but also important for students to input the target language. The quality of teachers’ instructional directives is closely related to students’ understandings and accomplishments of the tasks. In this study, English teachers’ instructional directives in the EFL classrooms of senior high school are analyzed and discussed with the methods of class observation and audio-recording. Six classes by two teachers at one of Beijing’s normal senior high schools are observed and four classes are transcribed into written materials. Based on the previous studies and the related theories-speech act theory and Krashen’s comprehensible input, a discussion on the sentence structures of instructional directives and the effects of instructional directives on students are made. The major findings are as follows: 1). As for the sentence structures of instructional directives, six sentence structures are included: direct instructional directives-a) (You) VP (please), b) Let’s …, c) Abbreviated instructional directives; indirect instructional directives-d) Can you/Could you/Would you …, e) Declaratives and f) Declaratives + tag questions. The result shows that the use of direct instructional directives is much more than the use of indirect instructional directives. 2). As for the effects of instructional directives on students, (You) VP (please) and abbreviated instructional directives are simple and clear which can save time and are easy for students to understand，but (You) VP (please) needed to concise enough and abbreviated instructional directives should not be used too many; Let’s… and Can you/Could you/Would you … are polite and moderate which are likely to be accepted by students; Declaratives are helped to instruct the class and explain things to students and declarative + tag questions can check students’ comprehension, but declaratives need students to have a better English proficiency and declaratives + tag questions are limited to several kinds of comprehension checks. In this study, according to the findings, some suggestions on giving effective instructional directives are also given to high school English teachers and they are hoped to have some help for senior high school English teaching.