Abstract: Reservoir submerged area is directly related to the immigration relocation scale and cost of a hydropower project. However, there are different methods calculating the reservoir submerged area around the world. The lacking of unified international specifications and standards restricts the development of new hydropower energy in international hydropower construction market. Based on the background of hydropower projects in Nepal, the determining method of reservoir submerged area was studied through field investigation, and we compared it with Chinese standard. It shows that there are significant differences on the design results by Chinese and Nepalese standard specifications. Chinese standard of calculating reservoir submerged area is more scientific and the design results are more accurate, which helps to reduce or avoid risks during implementation.