Abstract: Based on the theory of elasticity in combination with the loading conditions for a prestressed steel reinforced concrete beam, the differential equations are given to theoretically calculate the relative slip between the surfaces of concrete and corroded steel under uniformly distributed load, where the prestressed increment and corrosion rates of both steel and bars are all taken into account. Discusses the influences of the corrosion rates, loading and prestressed increment on the relative slip, thus giving the simplified slip calculation formulae. Calculated results showed that the slip increases with corrosion rate of steel and loading, but the corrosion rates of bars and prestressed increment affect the slip nonobviously.