Abstract: During the construction of Xiaowan hydropower, based on field investigation, project researchers analysed and checked orientation and property of every controlling structural planes in the water-intake slope, and determined seven movable blocks. Based on the block theory, this paper calculated stability coefficient and anchoring force of every movable block. The result shows that the main block controlling the stability of the water-intake slope is located on south side of the f89-1 fault. Its lower limit anchoring force is 351029 kN. Based on this anchoring force and the result of 2D limiting equilibrium analysis, the total anchoring force of the water-intake slope is determined as 516121.5 kN. It is evidently less than the former result.