Under the salt frost environment， the flexural behavior of reinforced concrete was studied. The bearing capacity and deformation performance of the beams were analyzed by comparing with the reference beam(undamaged) and beams subjected to 25，50，75 and 100 salt freeze-thaw cycles respectively. The results showed the plane section hypothesis still was satisfied for the concrete strains of frost beam section, and the mechanical characteristics of frost beam was similar to reference; The main reason to affect the beam bearing capacity under salt freeze-thaw environment was the concrete cover scaling in the compressive zone. Secondly, it was the reduction in concrete strength, while the degradation of bond properties between rebar and concrete was not a dominated factor; the deformations of concrete beam increased mainly due to the reduction in concrete strength, the damage of concrete cover and the degradation of bond properties. In addition to the number of freeze-thaw cycles, the positions of freeze-thaw damage and the load level affected the degree of reduction in beam stiffness.