Based on the synthetic method of rainfall attenuation time series, the dynamic rainfall attenuation time series at 28 GHz、30 GHz and 38 GHz in Beijing are simulated, and the power spectraare estimated by using fast Fourier transform and Kaiser Window function. The probability distributions of rainfall attenuation are obtained by simulating rainfall attenuation events for many times and statistical analyzing of the simulation series. Compared with the model recommended by ITU-R, it can be used for the prediction of 5G millimeter wave rainfall attenuation.