Abstract: In accordance with the experimental results, the contraction angles of the abutment walls on both side of side upper outlet are increased from 8°to 11.314°, and the end of the abutment wall is extended 3 m. The top elevation of the end of abutment walls is increased from160 mto 165 m. Thus, it is basically not to change the original design type, and the nappe is basically not to scour the slopes.