Effects of salt crystallization of Na_2SO_4 and NaCl on concrete exposed to drying-wetting cycles were investigated by using index including concrete scaling amount,concrete expansion rate and strength loss rate,and chemical attack of concrete soaked in Na_2SO_4 and NaCl solutions was also measured.The test results show that the deterioration of concrete caused by salt crystallization is much more severe than that caused by chemical attack.The scaling and expansion of concrete due to the action of salt crystallization significantly increase with the increase of salt concentration and number of drying-wetting cycle,and the concrete after drying does not shrink but expands when the number of drying-wetting cycle is over a certain value.The salt crystals have some compacting and strengthening effects on the concrete at first,and the expansion and deterioration of the concrete occur only when the amount of salt crystals is over a certain value.The salt-crystallized deterioration of concrete is significantly mitigated by airentraining.