Through the analysis of 12 typical thunderstorm processes around Shengxian County of Zhejiang Province recorded by the atmospheric electric field instrument from June to October 2007, in combination with the data recorded by lightning position finders, it is found that when thunderstorm clouds approach the station with an electric field instrument, there will occur the phenomenon of fastchanging dither before the occurrence of lightning within the protection range of the station (10 km around the station), which has the 01 relationship with lightning. That is, when the fastchanging dither in the electric field appears and the strength of the electric field reaches a certain threshold several times in a period of time, the electricfield strength will increase to achieve the intensity necessary for the appearance of lightning within the protection range, and there is little circumstances that the appearance of fastchanging dither is not accompanied by the appearance of lightning. The forecast equation and most appropriate electricfield parameters are given, and the method of thunderstorm warning is presented with the multivariate regression method. The results show that it is the best time to make warning when lightning strokes are concentrated within a range of 10 to 15 km around the atmospheric electric field instrument if the conditions of warning for the electric field instrument are satisfied, with the accuracy being up to about 73%.