The environment of hydraulic concrete is special，and the impervious performance of concrete is higher.Aiming at the limited ability of reinforcing agent to improve the strength of concrete.Research the influence of different spraying time and different concentration of calcium hydroxide on the protective effect of concrete，the specimen of 1 d，7 d and 28 d were enhanced by using reinforcing agent，0.166%，0.083%，0.04% calcium hydroxide solution and water to pre wet the hydraulic concrete，so as to determine the optimum spraying time and saturated concrete surface.It can be seen from the results that the effect of spraying increases with the decrease of concentration of calcium hydroxide solution，and decreases with the prolongation of spraying age.When the saturated solution is 0.04% calcium hydroxide solution and after 1 d，spraying enhancer can make the reinforcing agent achieve the best protective effect.