Based on the synoptic pattern classification and the principles of the Perfect Prognosis method, the thunder/lightning potential forecasts in Guangzhou are studied by using the lightning positioning data, conventional meteorological observational data, operating numerical model output and NCEP/NCAR reanalysis data during the period of 2000 to 2005. By the method of mosaicization of synoptic situation, the concept of uncertainty,and the statistical and mathematical methods such as regression analysis,the synoptic patterns are classified when thunder/lightning occurred；then the functions between meteorological elements and lightning times for each day are developed;accordingly the probability of thuncler/lighting occurence can be obtained. This operational scheme for thunder/lightning potential forecast is running in real time in Guangzhou Central Meteorological Office,which can provide some valuable references for thunder/lightning forecasing.