This paper analyzed the application of data mining in intrusion detection system based on a research on IDS,data mining and the types and limitations of traditional detection methods.According to the characteristic of IDS,it was pointed out that these limitations could be overcome by the data mining technology.The intrusion detection technology improved and optimized the association and cluster rules,which resolved its own disadvantages,including its inability to presage the number of the best cluster and its fine classification.Such an improvement reduces omissions and misstatement,and improves the efficiency of IDS.Experimental results show that this algorithm is feasible.