Abstract: The time variable gravity in Wenchuan and its surrounding areas was calculated by using the GRACE data published by UTCSR.Then the multi-scale wavelet analysis was used to decompose the satellite gravity field,therefore,details and approximations reflecting different depth of geological bodies were obtained.By studying changes in the gravity field of every detail and approximation component,combining with the features of regional tectonic movement,a preliminary explanation and discussion on the features of time variable gravity as well as the dynamic mechanism of Wenchuan earthquake was presented.The results show that the change in gravity which caused by the tectonic deformation and deep mass transfer in Wenchuan area is revealed effectively by the fourth-order detail and approximation.Moreover,the features of changes in gravity before earthquake meet the conditions of earthquake preparation and occurrence.