Based on chloride diffusion and random field theory, an analytical model of PC structures in erosive environment with chloride corrosion subjoining cyclic freeze-thaw was formulated. Models presenting the influence of chloride and cyclic freeze-thaw to failure probability are used to track the structural failure. It is found that cyclic freeze-thaw could be the driving force to damage of concrete in rigidity and mechanics. The computing results show that reliability index increases with the cover thickness, and cyclic freeze-thaw increases with decrease reliability. It is important to reliability calculation whether considering cyclic freeze-thaw.