This paper estimated the loading of nutrient sources for evaluating the potential of eutrophication in Sun-Moon Lake Reservoir. Analysis results show that the total phosphorus and total nitrogen loading approximated 1.86×10^4 and 9×10^5 kg/yr, respectively. The predominant loading source comes from the trans-watershed diversion of Wu-She Reservoir. The strategies of water pollution control include straightening the non-point sources in Wu-She Reservoir and reducing the nutrient loading of nitrogen and phosphorus into Sun-Moon Lake Reservoir, thus improving the water quality. If the total phosphorus capacity falls to 2.64×10^3 kg/yr, the reservoir will restore its mesotrophic status.