Abstract: Based on the meaning presented by transmissive indirect economic effect and obtainable indirect economic effect, the drive effect and the propel effect of each department on national economy are studied, and a classification index which classifies the effect of each department of national economy into variant types is given. According to the data of input-output of the Sichuan province from the year 1987 to 1997, the variation of the drive effect and propel effect of each department on Sichuan national economy for ten years are analyzed quantitatively. It is found that the type of each departmental effect is not constant, but various with the development of economy.