Abstract: The check-dam is an important measure for controlling soil and water loss in Loess Plateau. However, because of the lack of monitoring data on early built check-dam, the estimation for sediment volume trapped by full-filled check-dam becomes a difficulty issue. A check-dam built in Yangjuangou watershed in 1979 was taken as a case, which located in Baota district, Yan’an city, Shaanxi Province. By using high precision differential GPS technique, the average elevation of sediment surface and the silt area were measured. Based on 1997’s topographic map at scale 1︰10 000, the elevation-area/ sediment mass curve was obtained. The results indicated that the volume of dam-trapped sediment was 155 849.2 m3 (1979-2004) in Yangjuangou watershed, and calculated soil erosion modulus was 4 052.1 t·km-2·a-1, which belonged to the degree of moderate erosion. Application of differential GPS technique for estimating sediment volume provides technical support for accurate estimate of sediment volume trapped by check-dam, which can make up the data of erosion and sediment during history, and present the evidence on quantitative evaluation of soil and water loss and its controlling benefits.