Abstract: To quickly and accurately know the trend of cotton insect pest and improve the timeliness and accuracy of forecast, we applied data mining technology using association rules in Apriori algorithm to comprehensively analyze the occurrence trend of three kinds of cotton pests including cotton bollworm, cotton spider mites and cotton aphid. The results showed that the occurrence of the three major cotton pests had a close relationship with climatic factors. In particular, the changes of temperature directly affected the species, period and amount of pest occurrence. Data mining technology using association rules plays a very important role in dealing with a large number of agricultural information data. Apriori algorithm is a new technology in forecasting cotton pest and has broad application prospect.