Abstract: The rusting of carbon steel causes the degradation of the mechanical properties of the steel, leading to early withdrawal of the structure from work and seriously affecting the long-term performance of coastal infrastructure. A combination of experimental and numerical analysis was used to study the changes in mechanical properties of carbon steel in the marine environment. The corrosion and mechanical properties tests were carried out on 48 Q235 carbon steel specimens to obtain the degradation pattern of mechanical properties of carbon steel with different rust rates. A random rusting model of carbon steel was established based on Monte Carlo principle, and the mechanical properties of rusted carbon steel were numerically analyzed using finite element software. Comparing the numerical simulation with the test results, the results show that the average error between the numerical analysis results and the test results for the nominal tensile strength of carbon steel specimens with different corrosion ratio is 4.20%, and the average error for the nominal field strength is 6.38%, the results are in good agreement and the validity of the model is verified. The yield strength and strength limit degrade significantly as the corrosion of the carbon steel specimens increases.