Concrete is one of the important building materials, and studying its durability is crucial to ensure structural safety. In this paper, concrete with a strength grade of C40 and water-cement ratio of 0.42, 0.38 and 0.34 is taken as the research object. The deterioration of macroscopic properties (mass change, strength erosion and sulfate ion intrusion depth) under the coupling of dry-wet cycle and sulfate erosion is systematically discussed, and the microstructure evolution characteristics are analyzed by scanning electron microscopy (SEM). The results show that the mass growth of concrete with different water-binder ratios is positively correlated with the number of erosion cycles, and the mass increase of the 0.42 water-binder ratio concrete in the early cycle (0.436%) is 4.8 times that of the 0.34 water-binder ratio concrete group. With the increase of the number of cycles, the compressive strength of concrete shows a trend of first rising and then falling. SEM results show that the microstructure evolution of concrete in the environment of alternating dry and wet sulfate erosion is highly dependent on the water-binder ratio; due to the large porosity and loose structure, high water-binder ratio concrete is more likely to generate corrosion products and induce microcracks during the erosion process, resulting in a significant aggravation of deterioration. The results can provide microscopic basis and theoretical support for the durability design, material optimization and life prediction of concrete structures in dry-wet cycle-sulfate environment.