Experiments of five prestressed concrete beams after different times of freeze thaw were carried out to investigate the load bearing property of specimens. Based on the test data and previous work in concrete after freeze thaw, the formula of βn，α′n，ξb has been established after n times of freeze thaw. Comparing the values of theoretical calculation with experimental values, the conclusion that the calculation formula can reflect the general law of flexural bearing capacity of prestressed concrete beam normal section after freeze thaw effect has been verified.