This study explores the reasons for communication and dialogue can be established in Taiwanese society with multiple languages and ethnic groups, even though the languages used in three-generation families are different. Furthermore, learning more about the coexistence of multiple languages in the above-mentioned families is also a purpose. To complete this study, field survey was conducted last September and December in Taiwan. The differences between the languages and the languages used by three-generation family are also the observation standards. When choosing the three-generation families, the languages, the composition of the ethnic group, age, occupation, education level, economic status, living environment, and balance of classes were taken into consideration. From a sociological point of view, this study uses the ethnomethodology for dialogue analysis, and assumes the families share a silent understanding to the basis of communication and dialogue. This study also observes daily conversations of different nationalities which use different mother languages in one family.On the other hand, from the perspective of linguistics, code-switching is also a focus of this study. Through the analysis, a total of seven observations, fourteen interviews, and five field surveys were conducted. And it was found that different ages, classes, occupations, living environments, education, and growing environments cause the differences of the respondents' languages. For example, a family composed of two identical ethnic groups, can use significantly different languages. In addition, this study analyzes the content of the dialogue through the ethnomethodology. After transcribing a taped the shooting videos, it turns out that the respondents believe their own code-switching is only based on silent understanding, which is not absolutely correct. On the contrary, there are other factors that they may not have noticed, but constitute the cause of the status and role in between the members from the interaction.