The language attitude of Khmer people in informal communication in Soc Trang province is a topic in the field of social linguistics, which studies Khmer people’s attitudes in using their mother tongue and the Vietnamese language in informal communication, especially their mother tongue. The language attitude is expressed mainly in the scope of family communication and in that of social communication. As far as family communication is concerned, Khmer people often use language to communicate with grandparents and parents, with descendants, and with relatives and guests. In terms of social communication, Khmer people frequently use the language to communicate in some familiar places such as markets, bus stations, shops, supermarkets, and cultural venues. In addition, Khmer people also use language to communicate in some other cases such as talking on the phone, praying and worshiping, singing, singing a lullaby, etc. Surveys, quantitative and qualitative data, combined with observations and in-depth interviews show such results as: Khmer people in Soc Trang hold respectful attitudes with the sense of conservation and preservation of their mother tongue in the multi-ethnic and multilingual context, which is a completely voluntary attitude originating from the needs of real communication of the locality. In addition, the survey results show that Khmer people also show respect for the Vietnamese language. The Vietnamese language and the Khmer language are an important means of communication in Khmer people’s natural and social life. Each language has a different role and position in the social and family communication environment.