The academic exploration of teacher' code-switching in EFL classroom is significant in the following aspects：

First of all, code-switching is a very common phenomenon of EFL classroom at all levels in China. It seems so traditional that only a few teachers realize they alternate languages. Most of them have no awareness how, when, to what extent and for what purposes they actually switch languages in their teaching practice. This study intends to develop the teachers' conscious understanding of the principles underlying foreign language teaching and the practical techniques that teachers can use in different kinds of lessons. 

Secondly, code-switching study in EFL classroom may complement the code-switching theories by the researchers. Most researchers are concerned with the natural discourse in bilingual or multilingual speech communities, while only a few are concerned with the institutional discourse in language classroom. Classrooms do have their own rules of standards and norms which both teachers and learners share. A systematic description of code-switching in EFL classroom will help better understand the mechanism of classroom code-switching.

Thirdly, classroom code-switching in foreign contexts need to be tested or improved in Chinese context and may provide useful cues for foreign language (FL) classroom teaching and learning. There are numerous researches in addressing the question of the ideal roles of learners' L1 in bilingual and FL class contexts. How are these studies conducted effectively in Chinese contexts? Or are there any specific characteristics in FL teaching? The present research is going to pursue these questions and try to raise the awareness of both teachers and students on the issue of code-switching to make our FL teaching effective. 

And finally, this research would give guidelines and confidence to the teachers in secondary EFL classrooms, especially to the teachers in rural areas where the major basic English teaching will be practiced. It is also hoped that the findings in this research will give educational authorities a reference for language policy development. 

As to the reasons and significance mentioned above, code-switching in EFL classrooms is a significantly interesting topic. This study will narrow down the discussion into relatively small scope. That is, it will focus on teachers' code-switching in secondary EFL classroom in Chinese context, especially how teachers switch languages and for what purposes. A systematic description of code-switching in Chinese context will help better understand the mechanism of classroom code-switching in China. Eventually, we hope to develop the teachers' conscious understanding of the principles underlying foreign language teaching and give some practical techniques that teachers can use in different kinds of lessons. It will offer a more comprehensive look at the practice of code-switching in EFL classroom. 

1.3 Research questions

This study seeks to discover when and where the teacher make the switches and what makes these switches in her language teaching, especially what the teacher do with these switches or for what purposes. That is, this study is going to pursue the functions of code-switching in teacher's discourse in terms of communication and pedagogy in secondary EFL classes. Meanwhile, what are the related social variables that influence teachers' code-switching? How could the teachers avoid these negative influences?

This aim will be reached by solving the following problems：

1. How many types of code-switching exist in the process of secondary school English teaching? Which types are often used in class?

2. What kinds of functions do code-switching fulfill in the teaching? 

3. What are the factors that could influence the teacher's code-switching?

1.4 Organization of the thesis

This thesis mainly states the phenomenon of code-switching and studies the main types of code-switching in secondary school English classrooms, functions of code-switching, and the influence factors of code-switching on teachers' code-switching. Chapter One mainly introduces the research background，research purposes and significance, research questions and thesis organization. Chapter Two illustrates the basic notion of code-switching and the literature review about relevant research abroad and in China. Chapter Three is the research design, including the research subjects, research instruments, procedure as well as the research hypothesis. Observation, questionnaire and interview are used to collect the relevant data. Chapter Four displays and analyze the data results, and tries to give a comprehensive discussion. Chapter Five is the conclusion of the thesis. In this part, the author will also point out the major findings, pedagogical implication and shortcomings of the whole thesis. 初中英语教师语码转换个案研究(3):http://www.751com.cn/yingyu/lunwen_50804.html