The rheological structures of tectonic units related to Wenchuan earthquake is estimated based on geological and geophysical field data, as well as experimental P-velocity and creep data. There are two to three plastic layers in western Sichuan plateau and Longmenshan tectonic zone, but it is almost no any plastic layer in Sichuan basin. It plays a significant role for the complicated rheological structures to accumulate the tectonic stress and forming Wenchuan earthquake. The high temperature and high pressure experiments show that the strength of rocks is very high in earthquake source (mainly granitic rocks, such as adamellite), which could sustain great different stress and accumulate huge energy. This is one of major causes for high-angle reverse fault slip and high intensity of Wenchuan earthquake. However, high fluid pressure is a necessary condition for sliding of high-angle reverse fault and triggering Wenchuan earthquake, and Longmenshan tectonic zone might have provided with the requirement.