Abstract: Using NCEP 1°×1°reanalysis data and lightning monitoring data of Sichuan lightning location monitoring network system, Based on three kinds of forecast factors of Sichuan lightning potential forecasting decision tree, in allusion to the persistent lightning activity process in the northwestern Sichuan Basin of September 23rd to September 25th, 2008, special analysis the circulation background of persistent lightning activity and main weather system, thermal structure characteristics, dynamic characteristics, test the prediction ability of lightning potential forecasting factor which selected by decision tree method on the persistent lightning activity process. The result shows: 1) in persistent thunderstorm weather process of September 23rd, there are convective thunderstorm and thunderstorm period under the common action of subtropical high and surface cold air. Thunderstorm area always has a high- energy unstable thermal condition, which has typical characteristic of thunderstorm dynamic by the middle and low troposphere positive vorticity, negative vorticity in the upper troposphere. 2) Three kinds of forecast factors of lightning potential forecasting decision tree can effectively forecast the lightning activity.