When the traditional grey prediction method is used to model and simulate variation in seismic wave intensity, the series of the variation is predicted without analyzing the time attribute of earthquake wave intensity. Hence, the accuracy of the analysis result is low. A new mathematical modeling analysis and simulation method for these variations is proposed in this paper. The threshold value of the threshold autoregressive model is determined by the empirical distribution of the seismic wave intensity series. The threshold autoregressive model of seismic wave intensity series is obtained by using the threshold value of the minimum criterion AIC and the least residual square method. The characteristics of limit cycles and oscillations of the auto-regressive model are analyzed, and the seismic wave intensity is obtained. The mathematical model of seismic wave intensity series is constructed based on the mean generating function. The time series of the earthquake wave intensity is fitted by using the mean generation function. The fitting period is selected based on the double score criterion according to the time series. An accurate numerical simulation of seismic wave intensity is realized. The experimental results show that the proposed method is accurate and stable for the seismic wave intensity variation model.