| Yangtze River is the longest river of our country, but the Soil Erosion of mountainous areas that covers 70～80% of the watershed is serious, which directly affects the economic development of the whole basin. The Three Gorge Project (TGP) of China necessitates the resettlement of over one million population (mostly farmers) to more mgged and isolated areas than their original settlements, which cause great change of the landscape, moreover, the unreasonable landscape is one of the main reasons that cause the Soil Erosion. Therefore, it is especially necessary to explore the Soil Erosion in the Three Gorges storehouse district. In this paper, a case study was carried out in the representative small basin in the Three Gorges area. based on the summary of Soil Erosion studies in the watershed, Soil Erosion simulate model development and research front questions. According to the GIS technology and the theory of water and soil conservation, in the small basin foundation geography database foundation, the sediment is simulated through the Soil Erosion model, the rule of producing the sand in basin area is analyzed through the comparison of the sediment in different landscape. The main results are as follows:First, the ME (model efficiency coefficient) of the AnnAGNPS model is different from the ideal coefficient(1). The reason may be that the AnnAGNPS model adopted many experience and semi-empirical formulae. Without considering the rub power of current, the effective transportation of the channel sediment was greater than that of the sediment coming from the eroded, so the simulate result is on the high side systemic. In addition, the vegetation of the watercourse fixed some of the bedload, while the AnnAGNPS model supposed that the bedload would not stay in cell. Meanwhile the AnnAGNPS model didn't take the spatial difference of rainfall in into account, so the study adopted uniform rainfall parameter as well as uniform parameter of subwatershed, which was different from the fact of the watershed.Second, WATEM/SEDEM model is established based on the loess region in the middle of Belgium. In this area, hypsography is comparatively gentle, and the land use patch is comparatively big. The main Soil Erosion is slope erosion and rill erosion, but a small quantity of gully erosion is mainly temporary gully erosion. Thus, this model takes little consideration in gully erosion, especially the permanent gully erosion. Wangjiaoqiao basin is situated at the Three Gorges area, with many steep mountains, fragmentized rock mass, complex land use type, high intensity rainstorm in summer, so gully erosion is very easy to occur. Therefore, it can be seen that the tremendous difference in climate and natural geographical characteristic in the research area, has limited the application of WATEM/SEDEM model in the Three Gorges areaThird, Tiny erosion (57.7%), takes a great part of the Soil Erosion in the basin, terribly intensive erosion, intensive erosion and acute erosion accounts for a little proportion, 11.2% in all, moderate erosion and light erosion accounts for 22.1%. The annual mean sand production in the basin is 41153 ton, and the sediment modulus reaches 2464t/(km~2·a), which makes it belong to the light erosion area. According to this proportion, we can see that the soil and water erosion has been under effective control in this basin. However, the total Soil Erosion in the basin is often depends on the terribly intensive erosion area and intensive erosion area which occupy little part of the area. In Wangjiaqiao basin, tiny or light erosion area accounts for 67.9%, but the contribution ratio to Soil Erosion is only 3.6%. Meanwhile, 80.3% of the basin sediment comes from the area with terribly intensive erosion and acute erosion which occupy only 14.3% of the basin area.Forth, The flows pad surface of the construction was heavily compacted, and it's not easily to lead the soil erosion, so the quantity of the flows was the lowest, 209 t/(km~2·a). The surface soil of the slope cultivated land is soft, further more, it's have no good protection of plants, the raindrop directly falls on the surface soil lead to point erosion when it's raining, after conflux, the point erosion become to surface erosion and stria erosion. The soil grain has the migration with the current of water, so the quantity of the flows was the highest1566 t/(km~2·a), belongs to the fierce erosion area. The terraced field surface soil also directly receives the rain water pitting, but the intension of runoff must be much smaller than the slope cultivated land even in the continuous and heavy rain situation, because its slope nearly is 0. Therefore the terraced field produces the sand 235 t/(km~2·a), is only about slope farming 1/65. Because of the influence of the crown level of the Dense tall, sparse tall the bush and the orchard, the rains was temporarily stopped, so the power of the erosion weakens, the produced sand is lower than the slope farming obviously. The sand quantity 5121 t/(km~2·a) of the orchard produces belongs to the intensity erosion, the reason possibly is the big distance between the orchards, so the partial surfaces was directly corrosioned from falling, And in the mid-slope and small-slope area, it was planted directly, there is a lack of the effect water and soil conservation measure, therefore creates certain soil erosion.
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