Code-switching is a daily affair in multilingual communities. A set of negotiation system exists in the conversations made by speakers and hearers, which is used to test whether the participants have such kind of linguistic repertoire to handle code-switching, in order to take different conversation strategies to keep the conversation going on or to end it. With the assistances of several ways of analysis applied, including fieldwork and conversational analysis, this paper focuses on the social motivation and pragmatic model of code-switching between Cantonese and English.