In this paper, an empirical Green’s function method is used to simulate the near-field seismic characteristics of the Tonghai Ms7.8 earthquake that occurred in 1970.The various uncertainties in the source section are considered carefully. The strong ground generation area is introduced into the source model. A mixed source model to consider the uncertainties of the asperity is also established. Through ground motion simulation with small earthquakes occurring in Tonghai, the seismic characteristics of a large earthquake could be reproduced. By considering uncertainties, a source model for predicting future destructive earthquakes is established to provide a better scientific basis for earthquake prevention, disaster reduction, earthquake fortification and urban planning.