This research discussed about the occurrence of Indonesian-English code switching phenomenon happened in online class of English Department with Critical Discourse Analysis subject. The study focused in analysing the types of code switching and the reason why the speaker code switch in the online class. This research was classified as a descriptive qualitative research. The data was presented in the form of utterances spoken by the speakers in the online class. The result shows that there are three types of code switching appeared namely intra-sentential code switching, inter-sentential code switching and tag switching. Meanwhile, there are five out of seven reasons why the speaker code switch, namely talking about particular topic, intention of clarifying the speech content for the interlocutor, repetition used for clarification, quoting somebody else, and interjection. It is found that the speaker tends to switch the language in the middle of the sentence to mention the intended term which are mostly specified in talking a particular topic of Critical Discourse Analysis.

Keywords: sociolinguistics, bilingual, code switching, online class, reasons