Abstract:According to the data of lightning location system of Jiangsu province, this article analyzes the regulation of the lightning flash of Jiangsu province in 2005, and along with the sounding data of Nanjing, the situation of the lightning flash within the domain of 1°×1° grid around the city ,and within the time interval during releasing balloon-sonde twice a day. The results showed that the factors such as Showalter index, difference of pseudo-equivalent potential temperature (θse) between 700 hPa and 1 000 hpa level, θse difference of 500 hPa and 700 hPa level, temperature of 1 000 hPa level and temperature of 500 hPa level, have more obvious effect on lightning flash early warning for Nanjing region. This article also defines the lightning flash index of probability, which gives primary forecast of the lightning flash. This article gives reference on surveillance of Nanjing regions thunder and lightning