This paper constructs a finite element analysis (FEA) method for the numerical simulation of characteristic earthquakes, based on the wide-accepted knowledge of the shallow crustal structure and dynamic boundary conditions at the middle part of the Longmenshan fault zone. The influence of parallel thrust faults on regional seismic activity is focused on and simulated with this FEA model. The results show that the characteristic earthquake model with strict recurrence interval is not suitable for the entire fault zone which contains three parallel faults. When the distance between the faults is less than 20 km, the applicability of the characteristic earthquake model to each single fault is attenuated with the distance between the faults decreasing. The results based on the distribution pattern of the profile in the middle of the Longmenshan fault zone reveal that seismic activity of the back range fault is relatively independent, and the characteristic earthquake model with strict recurrence interval is not suitable for the entire fault zone and the central fault.