Generalized topic structure (GTS) is the fundamental objective structure in Chinese text. We design a computational model to recognize this structure based on the idea of finite-state machine (FSM). We preliminarily prove its validity in large-scale corpus and analyze its spatial complexity and time complexity. The characteristics of this model are: iterative control, synchronization of output and input in punctuation clauses (P-clause), none backtracking in long distance, limited backfilling, limited storage, and unchanged lexical order. These features are also the principles obeyed by human being while cognizing the topiccomment information in text. Thus, this model can be regarded as a mechanical model of the cognitive process of human.