Abstract: In order to examine the effect of the rubber powder in the same volume replacing the sand in differentproportions(replacement rate) and the degree of rubber powder's fineness (fineness modulus) on concrete strength, it was used the double-factor repeating test method, that was, just to consider the replacement rate and the finenessmodulus, other test conditions to be maintained invariable basically. The analysis of variance shows that the amount of rubber powder has great influence on concrete's 7d and 28 d compressive and tensile strength, the fineness of rubber powder has great influence on concrete's 7d and 28 d tensile strength, its influence on the 7d compressive strength is significant, while it is not evident on 28d compressive strength, these two factors interaction has great influence on concrete's 7d and 28d compressive strength, its influence on 7d tensile strength is significant, while 28d is not remarkable. Regression analysis shows that the amount of rubber powder and the fineness have linear relationship with concrete's 7d and 28d compressive strength, so does concrete's 7d tensile strength, but they don't have linear relationship with concrete's 28d tensile strength.