Inversion tectonics has been considered as one of the main characteristics of foreland fold and thrust belts. One important parameter to describe the inversion degree of inversion tectonics is the inversion ratio, which is determined by comparing the apparent length along the fault-dipping direction before and after the inversion. The Jiangshan-Quzhou, Majin-Wuzhen and Hangzhou-Jiaxing-Huzhou cross section are selected to be discussed in Northwest Zhejiang foreland fold and thrust belt because they are distributed in the southwest, central and northwest cross sectional position, respectively. By calculating the inversion ratio and other synthetic analysing, we have found that an extensional realm that existed in the Palaeozoic period in Northwest Zhejiang had been transported into a compressional realm in the early Mesozoic time, and the degree of structural inversion decreases from southeast to northwest. Together with the spatial temporal distribution of the tectonic facies and structural styles in Northwest Zhejiang foreland fold and thrust belt, the authors conclude that the inversion tectonics is compatible to the tectonic vergence of Northwest Zhejiang foreland fold and thrust belt, and is probably due to a significant orogenesis which happened in Northwest Zhejiang in the early Mesozoic time.