The essence of common concrete durability design is to determine the w/c ratio and the minmal,cement consumption that can meet the demand of concrete durability,This paper adopts the formula method to directly design the mixture ration of concrete by analyzing durability while considering both strength and durability.Based on the deduction of the mathematical relationships of w/c ratio,unit cement consumption and concrete strength.f cu ,the formula of w/c ratio is established that meets durability index.Then ,comparing w/c ratio that meets durability with w/c ratio that meets strength,the lower one is chosen to calculate unit cement dosage by formula(4).In this paper concrete durability is divided into frost resistance durability,carbonization durability,acid radical diffusion durability and grinding durability.