To investigate the effect of aging of surface concrete on the internal and external humidity response of existing structures, experiments were conducted on carbonation, chloride salt erosion, and the rapid dehydration and reverse humidity response of concrete after their combined action in the marine atmospheric environment. The experimental results show that the peak water loss rate of concrete decreases first and then increases with the increase of carbonation age and chloride salt content. Among them, the peak water loss rate of concrete is the smallest when the carbonation age is 14 days and the chloride salt content is 1.5%. The water loss rate of concrete after the combined action of carbonation and chloride erosion is lower than that after the separate action of the two. The reverse humidity response of concrete shows a trend of first slowing down and then accelerating with the increase of carbonation age and chloride content. After the combined action of carbonation and chloride erosion, the reverse humidity response of concrete is slowed down compared to when they act alone.