Abstract: Accelerated corrosion test was carried out on Q235 steel plate in neutral salt spray corrosion environment for 0-178 days, and then the data of corroded steel plate surface were collected by using optical surface measurement technology to establish the corroded surface geometry model of Q235 steel plate by Geomagic studio. Degradation law of mechanical properties of Q235 steel plate were investigated by uniaxial tensile tests. The results show that yield strength, tensile strength and elongation obeyed a linear degradation with the increase of corrosion mass loss ratio, the yield platform became shorter rapidly. The corroded steel plate with big pits more easily entered its stage of necking because of plastic damage. By modifying the second plastic flow model, the stress-strain constitutive degradation model of corroded Q235 steel plate was established, and the degradation law of the model shape control parameters based on the corrosion mass loss ratio was achieved finally. In neutral salt spray corrosion environment, the main corrosion feature of Q235 steel plate was pitting corrosion, corrosion pit exhibited uneven distribution, separate characteristic and randomness, however, the effect of layered erosion could not be ignored.