The service structure in the complex salt etch environment of sulfate and chloride may be affected by the coupling effect of them. In this paper, the chloride penetration resistance (CPR) of the concrete half immersion in sodium sulfate solution (SSS) under capillary action is studied. The capillary rising test of mortar with different water-cement ratio and different concentration of SSS was designed. Scanning electron microscopy(SEM), X-ray diffraction (XRD) and electric flux of chloride ion are applied to the concrete half immersion in SSS. The results show that the CPRs of concrete samples half immersion in SSS deteriorates, and have obvious degradations at early stage, but recover a bit at later stage. Combined with the results from microscopic tests, the degradations are attributed to the SSSs filled in the pores of concrete samples. The SSS impairs the ability of bound chloride ion and releases more free chloride ions, which increases the electric flux of chloride ion. With the extension of soaking time and the change of the relative humidity of environment, supersaturate SSS comes into being Na₂SO₄ and Na₂SO₄·10H₂O crystals. The admixtures of crystals deposit on the walls of pores, and partially hinder the diffusions of chloride ions, hence increase the CPRs. When the concentration of SSS is higher than 5 percent, the velocity of capillary suction (VCS) slows down and the CPR of concrete is accordingly enhanced with the increase of the concentration of SSS. The VCS can be used to predict the CPR of concrete. The mixed solutions with sodium sulfate and sodium chloride can retard the VCS and then improve the CPR for concrete.