[en] A quantitative research about the effect of rainfall on gamma radiation monitoring data around nuclear power plants was carried out. First, according to the radionuclide measurement of rainfall, the key radionuclides impacting the gamma dose rate were found to be Pb-214 and Bi-214, the duration was about two hours after rainfull was over. Combining the relevant monitoring data with the decay of Pb-214 and Bi-214, the fitting equation for the effect of rainfall on gamma dose rate was obtained. The change of γ dose rate in rainfall can be predicted with the equation through inputting the first peak of the rain and γ dose rate in the case of multiple rain peaks. By applying the equation to the historical data including different rainfall intensities and different locations, the simulation results obtained were found to be consistent with the measurements. This method is meaningful to the real-time judgment of abnormal existence of artificial radionuclides in the process of rainfall around the nuclear power plant. (authors)