DEM, land use, soil, weather and other spatiotemporal data are combined with GIS, RS technology to build the SWAT (Soil and Water Assessment Tool) model for Erhai basin. The influence of land use change on runoff in 2000 and 2010 is analyzed and it is concluded that the rate of runoff change caused by land use change is 2.46% in Erhai basin. According to Overall Planning Framework of Land Use in Yunnan(2006-2020) and in line with land use distribution in Erhai basin, three land-use scenarios are set up. Simulation results show that in scenario 1 (66.06 km² farmland are changed into forestland and 89.16 km² farmland are changed into grassland), the simulated annual runoff increases by 75.73mm; while in scenario 2 (100.13 km² bare land and 105.74 km² grassland are changed into farmland), the annual runoff increases by 39.89mm; and in scenario 3 (138.72 km² grassland and 292.86 km² forestland are changed into farmland), the annual runoff decreases by 20.36mm. We also conclude that when the slope gradient is larger than 15°, increases in forestland and grassland will induce runoff increase, whereas when slope gradient is smaller than 15°, increase in farmland will reduce runoff to some extent.