Based on the on-site survey to Xiagongyan reservoir, conbined satellite image data and the forum with departments of water source management ,the paper analyzed the pollution situation of Xiagongyan reservoir. The results show that NH3-N has become the main factor of pollutant in Xiagongyan reservoir, the pollution indexes of COD and NH3-N are 16.61% and 83.39% respectively. Among the pollution sources, the size order of pollution indexes is agricultural >domestic >fish pond >industrial .Finally it put forward the corresponding countermeasures of prevention and control.