To optimize grouting design scheme of the left spillway for a power station, comprehensive survey was made for borehole arrangement and single borehole grouting tests were demanded. In order to ensure construction quality, the process flow was optimized, the equipment and personnel were strictly selected and single borehole grouting tests were made at representative regions according to the grouting specifications and design requirements, such as gate hoist, 2 sides of spillway and overflow weir with good grouting effects, which could be the basis for sound grouting design scheme.