Abstract: The topic chain is a common device of Chinese text organization, and its embedded parts play an important role in the topic chain hierarchy and text structure. Based on the relationship between embedded parts and topic chains, this paper explores the specific type and grounding function of the embedded parts. It is found that there are two embedded types: topic chain and embedded clause,and three functions are usually served, that is, information supplementing, scene- setting and narrative moving, the first two of which are backgrounded, while the last is foregrounded.