By the test of reinforced concrete columns in simulated marine environment under sustained load, the influence rules of stress level and test period were explored on transport characteristics of chloride ions. Using dry wet time ratio of 2∶1, concentration distribution characteristics of chloride ions were studied by the experiment of specimens with different stress levels for one year. The influence rules of stress level and test period were obtained on chloride ion transport process, surface chloride ion concentration, convection zone depth and the peak value of chloride ion concentration by data analysis. Formula was established to predict the chloride ion diffusion coefficient considering both stress level and test period. The influence of stress level was illustrated on the different transmission mechanisms of chloride ion in concrete under dry wet cycles.