Sempor Reservoir located in the Telomoyo River Basin in theSerayu River region is categorized as one of the priority watersheds based on the 2015-2019 Strategic Plan of the Ministry of Environment and Forestry. Priority watershed is a watershed that is getting more attention in controlling water quality, including sedimentation. Monitoring and management activities of the watershed are needed in order to get an optimal operation of the reservoir. One of the monitoring and management activities of the Sempor Watershed is the sedimentation rate calculation. In this research, the sedimentation rate calculates using the MUSLE method. The Sempor watershed boundary is defined through the delineation of DEM and satellite images data. The calculation of sedimentation is obtained by several factors, including runoff parameter, erodibility, length and slope, land cover, and conservation. The calculation is performed by a Geographic Information System (GIS) method through analysis of soil type maps, length and slope maps, land cover, and conservation maps. Based on the calculation result, the Sempor Reservoir has a sedimentation rate of 166.173,500 tons/year or 3,7259 mm/year in thickness. According to the provisions of the Ministry of Forestry in 2009, the sedimentation thickness rate of the reservoir is categorized in the medium class. The river as one of the potential means of sediment transport contributes to the rate of sediment thickness of 3,7256 mm/year, while for areas outside the river coverage it only 0.0003 mm/year.