The corrosion law of steel strand in chloride salt environment under different stress amplitudes was simulated by the salt spray corrosion test. The independent distribution form of long axis， minor axis and depth of erosion pit was obtained from the perspective of probability. Besides， the joint distribution model include the three parameters was set up based on the three-dimensional Copula function and the correctness of the model is verified by significance test. The results show that Clayton Copula function has high accuracy in simulating the distribution of pits. In addition， it is found that the tensile strength and elongation of steel strands decreased mainly caused by corrosion and then the fatigue life of steel strand will be reduced. The three-dimensional corrosion pit prediction model is conducive to further study of the corrosion fatigue life of steel strands.