nearby society, sometimes, they are divided by political boundaries, and some of them are identified similarly by nation or state (Wardhaugh, 2010).The phenomenon of code-mixing and code-switching are widely popular. The writer saw this phenomenon in her society, especially in a school she worked, the communication between the teachers and the students tend to mix and switch between English language and Bahasa Indonesia.In this research, the writer will analyze the interaction between a teacher and the students in Maths class by reason because Maths is taught in English by a teacher who the native language is Bahasa Indonesia. Since pandemic Covid-19, the learning-teaching sessions are done by online and the students did not come to school. Sihombing (2020) state that Covid-19 pandemic caused everyone to behave beyond normal limits as usual. The outbreak of this virus has an impact especially on the economy of a nation and Globally (Ningrum, 2020). The problems posed by the Covid-19 pandemic which have become a global problem have the potential to trigger a new social order or reconstruction (Bara, 2021). Code-mixing and code-switching are considered by doing language research in Maths class session.Many researchers have conducted research between code mixing and switching such as (Waluyo, 2017) analyzed the types, the effect and the reasons of using code-mixing and code-switching in English Grammar. The form of code-mixing in a vlog (Maghfiroh, 2018). On the other hand, (Sugiantari, 2018) did the research toward the factor of using code-mixing and code-switching by Government of Bali. (Karie & Husain, 2020) describe the used of code-mixing and code-switching by the types, factors and reasons in English Education study. Lastly, (Klapicová, 2017) observe social aspects of code-switching and code-mixing towards children.