Using a two-dimensional seismic attenuation tomography technique, the crustal Qs dynamic variation in Zipingpu reservoir area, Sichuan Province, was obtained by inverting S wave data from relocated earthquakes from 16 Aug 2004 to 11 May 2008 with the double-difference algorithm. The result shows that low-Qs region expanded and Qs value aroppeu significantly around the reservoir area during the first fast water-loading period. In particular, Qs value varied remarkably in the southwestern, northeastern and middle parts of the reservoir area. Monthly moving average Qs values for different-sized regions in the Zipingpu reservoir area decrease with elapsed impoundment time and increased water level, and the Qs value in the middle reservoir area dropped sharply.Furthermore, the impoundment enhanced seismic activity in the reservoir area, and mainly increased activity of small earthquakes of ML0. 0~2. 0.