As one of the most important study fields of global change, land use and land cover change has significant impacts on regional and global climate, soil characteristics, and function of terrestrial ecosystem. Most researchers, both in China and abroad, have given much more attentions to the study on land use types and the laws of regional land cover change with synthetic analysis of the factors that influence land use and land cover change. In recent years, some Chinese researchers have carried on studies in this field by stationary inspection methodology, e.g., Professor Fu Buojie and others studied the impacts of land use and land cover change on soil nutrients, regional hydrological condition in loess hilly areas and Zunhua low mountainous areas in Hebei province, Professor Shi Peijun and others studied the impacts of land use and land cover change on natural agricultural disasters in Inner Mongolia Autonomous Region on the basis of long period investigations and statistical materials. But few researchers studied the impact of land use and land cover change on soil erosion by stationary methodology, and few papers have been published in this area. This paper studied the impacts of land use and land cover change on soil erosion in Fujian mountainous areas on the basis of analysis on long period observational and experimental materials at Jianou Niukenglong Experimental Station and the Provincial Soil and Water Conservation Station, researched soil erosion mechanisms of mountain grassland ecosystem, and different soil erosion modulus under different land use and land cover types. The analytical results indicate that the coefficient of runoff has minus linear relation with grassland coverage, and the modulus of soil erosion has index relation with grassland coverage. This paper also studied the mechanisms and processes of land cover impacting runoff and soil erosion, i.e., land cover influences runoff and soil erosion through the following processes: 1) The grassland cover reduces the forces of rainfall that beats on earth surface, which will impact soil erosion on the surface of the earth, grassland cover has minus index relation with soil erosion modulus, and minus linear relation with coefficient of runoff. 2)The roots of vegetation strengthens the erosion resisting capacity of soils through interluding, twinning and fixing forces on soil particles, and increases the absorbing water capacity of soils . 3) The increase of soil organic material concentration makes the soil particles and structure more and more stable. This paper also points out that there are other mechanisms and processes that need to be further studied, e.g., the relation between land use/land cover and runoff coefficient, the variations of different vegetation's impacts on soil erosion,etc.