Abstract:Based on two periods of land cover maps derived from remotely sensed date, Landsat TM, CBERS and digital elevation model (DEM) derived from 1∶250 000 topographic maps. Studies on land use/land cover changes (LUCC) of Qingchuan county, Pingwu County and Maoxian county before and after Wenchuan Earthquake, and the influences of two importance cause of slope and aspect in ecosystem. The main results are as follow: after earthquake, the area of woodland, grassland and farmland decreased obviously by 92.09km2,46.98 km2 and 30.81 km2 respectively, open forest land increased by 98.81 km2 for area. The open forest land area changes amplitude is most, the value is 6.20%. Results indicated the ecosystem is degenerating and in study regions after earthquake, especially Qingchuan county. Topographic conditions are of great importance to the distribution of land use/land cover and the process of land cover changes. Under different slopes, there are large area changes of LUCC great than 35° because of earthquake. The order are 0-8°, 15-25°, 8-15° and 25-35°.These changes have obviously relation with earthquake and the secondary mountain disasters such as rock fall, landside, and debris flow. Aspect has a large influence on the distribution of land cover types, especially in half-shady slope; the order is half-sunny slope, shady slope and sunny slope. The area changes amplitude of land cover types are obviously in different aspect.