This paper studies different types of segmental lengthening in Mandarin Chinese by clarifying temporal structure of various lengthened syllables. The discussion is mainly based on an investigation to a discourse speech corpus. The results show that there exist three types of syllable lengthening in spoken Chinese, and each type is matched with certain prosodic events and characterized by certain profile of temporal variation. Therefore, segmental lengthening may be a valuable source of information in understanding prosodic organization of speech. It should be of benefit to recognize the mechanism of speech production and perception, as well as improving in speech recognition, synthesis and natural language understanding.