In order to study the influence of freeze thaw damage on the mechanical properties of concrete, rapid frost experiments were conducted on specimens with varied water to cement ratio and air content, then the tests of the flexural, compressive, tensile splitting strength and dynamical elastic modulus of frozen concrete were carried out. The dynamical elastic modulus was chosen as damage variables, the relationship between freeze thaw damage and flexural or compressive strength were analyzed, and an attenuation equation on flexural strength of damaged concrete was proposed through regression analysis. The experimental results show that flexural, compressive, tensile splitting strength and dynamical elastic modulus decrease with the increasing freeze thaw cycles; and the decay rate of flexural, tensile splitting strength and dynamical elastic modulus increases. On the other hand, the decay rate of compressive strength increases at first with the increasing of freeze thaw cycles, and then decreases. For the same freeze thaw cycles, the higher is air content or the lower is the ratio of water to cement, the less is strength loss. The descending order of loss of mechanical properties was as follows：flexural and tensile splitting strength, dynamical elastic modulus, compressive strength. The damage degree and the flexural strength were well correlated while its correlation to the compressive strength was weak. When damage degree is less than 40%, the compressive strength of freeze thaw damaged concrete is not lower than 70% of its original strength.