The effect of three boring pests, maize weevil，rice weevil and lesser grain borer, on amylase and peroxidase (POD) activity, and the variation was studied in order to provide quantitative parameters for grain storage scientifically. Some quantity of mixed wheat stored in Henan province for two years were taken as a test sample, which were to be infected by each kind of borers with different densities for different periods of time. The falling number and POD activity were measured at different infection time, the relativity with pest population density and infection time was analyzed. The result showed that the falling number was in the trend of increase and POD activity in the trend of decrease along with three main kinds of boring pests population density increasing and the infection time prolonging. The correlation analysis shows that the falling number was significant positive correlate with the infection time，POD activity was significant negative correlate with the infection time and the falling number, while both of them showed non-significant correlate with pest population density.