Featured with narrow river valley and large discharge, Baihetan hydropower project is faced with prominent problem of flood discharge energy dissipation. Three groups of asymmetrical surface spillway were adopted to prevent from the overlapping of discharge flow in the limited space. Model tests have shown that in original design scheme, even though the discharge flow disperse effectively with surface or deep hole discharge, the dynamic impact pressure in plunge pool with surface and deep hole combined discharge still exceeds conventional standard, which may affect the safe operation of the plunge pool. In view of this, according to the characteristics of collision of flows from surface spillway and deep orifice, we adjusted the depression angle of the surface spillway to improve the collision effect of water tongues, and meanwhile adjusted the plane deflection angle of the deep orifice to improve the dynamic impact pressure distribution in the plunge pool with high power discharge. The optimized asymmetric arrangement is effective in energy dissipation while ensuring the safe operation of the plunge pool.