Though acting as very productive morphemes, the Chinese quasi-prefixes “fei” and “wu” have received inadequate attention in the studies of Chinese morphology. The current research, drawing on extensive corpus data, identifies the structural hierarchy of lexical units with “fei” and “wu” as quasi-prefixes through examination of corresponding syntactic, semantic and prosodic structures, analyzes their structural meanings within lexical units, and further explores their difference in word formation and the reasons for such difference. Our findings can provide a new model for analysing lexical units with “fei” and “wu” as quasi-prefixes, which may be applied to improve automatic word segmentation and part-of-speech tagging in Chinese information processing.