The dykes of curtain grouting work area in Dagangshan hydropower station are steep and the environmental limitation and natural deflecting force of formation are significant. So the design of hole-deflection is strict and the vertex angle requirement is up to ≤ 0.5 °/100 m. By using multi-stabilizer anti-deflection BHA, the grouting hole axis vertex angle changing and hole bottom offset were effectively limited and the grouting hole bending deflection was controlled with the quality of grouting holes significantly improved.