Based on digital seismograms recorded by Zipingpu reservoir digital seismic network and YZP station of Chengdu Digital Tele-seismic Network from August 2004 to May 2008 before Wenchuan MS8.0 earthquake,the seismic source parameters of 261 earthquakes above M 1.6 are calcalated.The result shows： seismic moments Mo were 1.35×1012~5.98×1014 N·m;the stess drop increased with earthquake magnitude;and the relationship of corner frequency relying on seismic moment and earthquake magnitude was not come into existence in Zipingpu reservoir area.This may have relation with augment of pressure,pervasion and infiltration of water along Longmenshan fault belt after reservoir sluice.