Abstract: Based on the theories of continuum mechanics and block dynamics, the present study primarily analyzed the tectonic stress field of the main shock faults in the Wenchuan Ms8.0 earthquake happened on May 12, 2008. It discussed the interactions between block-block, block-fault, and fault-fault. The results showed that the strain energy migrates along with the fault propagation. The displacement filed, stress field and the distribution of total strain energy, and the mechanism of the process of the earthquake is explored quantitatively. The results also showed that the Wenchuan Ms8.0 earthquake changed the tectonic stress field. There is energy concentrated area along the Wenchuan-Maoxian fault after the earthquake, so there should have energy release.