The invention provides a lightning activity data statistics method based on a modified Apriori algorithm. The method includes: 1, calculating weighted support and weighted confidence; 2, performing vertical bit vector format conversion; 3, generating frequent bipartite graphs; 4, mining candidate sets. Items are imparted with proper weights according to actual needs, and the original support and the original confidence are modified into weighted support and weighted confidence which are more practical. In addition, according to the algorithm, item information is stored in the bit vector vertical data format, storage space is saved, and I/O efficiency is improved; according to the modified algorithm, based on the top-down concept, longest frequent item sets meeting the support and confidence requirements are located through frequent bipartite digraphs, and all frequent items meeting the requirements are generated according to properties of the frequent time sets. Through the application of the algorithm, the efficiency of the Apriori algorithm is improved in terms of both space and time, and the algorithm better meets the actual needs.