Abstract: The selective Question "X or (Y)" has been extensively studied in linguistics, by grammarians in particular.However, the existing studies are mainly about the syntactic forms, semantic contents, and pragmatic functions of selective questions.Few studies are based on its occurrence in natural conversations, and even fewer studies have ever touched on the concept of preference.Based on recordings of natural conversations in Mandarin along with their transcripts, this study attempts to explore the preference for "X" in selective question "X or (Y)" within the theoretical framework of Conversational Analysis.The present study proves that the preference for the selective item X is a generalized and institutionalized method of speaking in Mandarin.