This research aimed to find the kinds of language variation and the reasons of code choice used by the students of Ma’had Walisongo. It is descriptive qualitative research by filling questionnaire, doing interview, recording and documentation. The data were identified according to the theory of Jendra to identify the kinds of language variation and Holmes to identify the factor that can influence code choice by students of Ma’had. From the research, I found senior students using Indonesian, Javanese, English, and Arabic in their activities. There are twelve kinds of language variation used by them, those are individual and societal, regional and temporal, native and non-native, spoken and written, formal and informal, standard and non-standard, upper and lower standard, women and men’s, restricted and elaborated, ethnic, professional field, and secret language varieties. They used code choice based on setting, participant, topic and function for showing respect, politeness, solidarity, closeness or understanding easier because of unitary language (neutral) and standard language. I recommend teachers to be aware of how to choose an effective language and to develop their competence in English teaching especially in the code choice and language variation. Students should also be aware of how to use it in every situation and condition. This result of research can be used by teachers to teach students in the material of expression how to greet, to thank, to take leave and apologize. For lecturers, it can be a reference in teaching code choice in Sociolinguistics subject. I hope the next researcher to explore more about code choice in the different subject.