Summary: The sudden big earthquake which happened in the Wenchuan county of China in 2008 was an extraordinary type of earthquake. Its exact mechanism is still unknown. The paper presents a simplified computational approach to develop a model to simulate the long-term evolution of the Wenchuan earthquake fault by means of a viscoelastic finite-element method, in order to investigate the dynamic mechanism of the 2008 Wenchuan earthquake. The relevant characteristics of crustal stress fields and displacement fields around the fault are analyzed. It is suggested that the accumulated earthquake energy was mainly due to deep crust motion rather than to surface motion. The study helps show that viscoelastic modeling is a powerful tool for simulating natural phenomena such as crustal movement and its implication for earthquakes.