Transport process of Na2SO4 solution in partially immersed concrete, where the upper surface of concrete contacts the solution and the bottom surface contacts air(like tunnel lining concrete), was stimulated, and the effects of relative humidity(RH), water cement ratio(mW/mC) and concentration of Na2SO4 solution on the evaporative ratio were observed. The test results show that lower RH and larger mW/mC cause faster evaporative ratio, but higher concentration of solution hinders water evaporation. These results cannot be reasonably explained by the classic theory of wick action. Micro analysis by NMR and XRD, shows that the formation of ettringite and gypsum due to chemical sulfate attack block the pores in the concrete and decrease the evaporative ratio. Higher concentration solution and higher RH condition can result in stronger chemical reactions and lower evaporative ratio.