Spray cooling is an efficient high heat flux cooling method. In this study, the heat transfer characteristics of the spray cooling with ammonia as coolant are experimentally investigated under different ammonia saturation pressures. The cylindrical copper acts as the heat sources with seven cartridge heaters, and two-nozzles arrays are specifically designed to spray with ammonia. Experimental results indicate that the latent heat of ammonia decreases with the saturation pressure increasing, it is useful to promote the single-phase convection to convert to the nucleate boiling at the lower superheat temperature. The surface temperature and heat transfer coefficient increase with the saturation pressure of ammonia increasing but the variation trend of the superheat reverses. The maximum heat transfer coefficient of 1.48×105 W/(m2·K) is achieved with the heat flux of 310 W/cm2, the spray chamber pressure of 4.01×105 Pa and the surface temperature only of 19.5 ℃. Meanwhile, this study provides a reference in the engineering application for the high heat flux cooling technology.