Based on analysis and measurement of a geostress field at the dam site of the Jiangpinghe Hydropower Station, and comparison of calculated and measured stress at the points for stress fitting, inverse analysis of the initial geostress field at the dam site of the Jiangpinghe Hydropower Station was conducted using a threedimensional numerical model with different boundary loading conditions. The results show that the initial geostress is low at the dam site of the Jiangpinghe Hydropower Station, the maximum principal stress is 2.5MPa and its direction is N45°W, and the minimum principal stress is 1.5MPa with a direction of N45°E. There is agreement between the calculated and measured stress at the points for stress fitting, indicating that the initial geostress field at the dam site obtained by inverse analysis is reasonable and conforms to the historical background of the geological structure.