Abstract：By using the GPS velocity fields of China mainland in three time periods since 1999, the characteristics of crustal dynamic evolution before Wenchuan Ms8.0 earthquake was studied. From the results following knowledges can be drawn.1)The Wenchuan earthquake had taken place in the zone where crustal squeezed movements were blocked obviously. There was a large obstacle existed in the seismogenic zone, and the fault nearby the epicenter was in strong blocking state for many years.2)With the Wenchuan earthquake approaching, the compressive zone in the west to epicenter gradually expanded to east obviously. In some local areas, the direction of principal compressive strain deflected northward, and right lateral shear slip enhanced obviously.3)The sectional features of coseismic deformation in Whenchuan earthquake and 6.0 or more aftershock distribution were closely related to the sectional movement deformation of the fault and its vicinal zone.
