Vocabulary growth research is based on the type-token-ratio (TTR) changes of the texts in different periods. This article selects Reports on the Work of the Chinese Government from 1954 to 2018, analyzes the curves of tokens and types in the texts, and explores the interaction between vocabulary richness of the reports and the policies. It first conducts Chinese word segmentation on the corpus and then selects the Heaps model for prediction according to different curve fitting effects. Taking China’s Five-Year Plan as the basic time cycle, the difference be-tween the predicted value and the observed value of each cycle is compared with that of the random texts. The study reveals that vocabulary growth with time changes shows a certain tendency: in the period of deepening reforms and launching new policies，more words are needed to describe the phenomenon and the observed value is higher than the predicted value. With the analysis of the diachronic changes of Chinese texts, this paper provides references for the study of Chinese vocabulary growth.