To investigate the durability of retard-bonded prestressed concrete beams under the combined actions of long-term load and corrosion, the corrosion tests on total 14 retard-bonded prestressed concrete beams and ordinary reinforced concrete beams were conducted under the combined actions of loading and dry-wet cycles of chlorine salt. The effects of load ratio, degree of prestressing action, and dry-wet cycle time on the distribution of chloride ion concentration along the depth of different sections and on the rule of corrosion of steel reinforcements, as well as the influence of load ratio and dry-wet cycle time on the chloride ion transport velocity, are summarized. The results show that the application of prestress in concrete beams can effectively slow down the penetration rate of chloride ions and enhance the corrosion resistance of members to chloride salt. The chloride ion concentration at the same depth increases with the increase of load ratio, the increase of dry-wet cycle time, and the decrease of the distance of the detected section and the mid-span section. The relationship between the chloride diffusion coefficient and the load ratio of retard-bonded prestressed concrete appears to be exponential. The action of load accelerates the process of reinforcement corrosion. In the case of the same crack control grade, the corrosion degree of the steel reinforcements of the retard-bonded prestressed concrete beam with a larger load ratio is equivalent to that of the non-prestressed beam, indicating its better durability.