Using ammonia as coolant, experiments are performed to investigate heat transfer characteristics and surface temperature distribution for the spray cooling of 350 W/cm2  high power solid state laser. When the heating power and spray height were constant, the cooling surface was mainly dominated by forced convective heat transfer, high inlet flow rate of liquid ammonia resulted in low surface temperature and uniform temperature distribution. When the volumetric flow was 0.461 L/min, the cooling surface temperature was only 2.6 ℃ and the temperature deviation was ±1.1 ℃, the heat flux dissipated could reach 388 W/cm2. As the inlet volumetric flow decreased, the dominant heat transfer mechanism for spray cooling gradually converted the forced convective heat transfer to the boiling while increasing heat flux, resulting in decrease of uniform temperature distribution of heat transfer surface.