In order to delve deep into the regularity of strength degradation of concrete in sulfate environment, a comparative study is done between static compressive strength, acoustic emission and scanning electron microscope (SEM) to understand the micro-level aspect of concrete specimens which have been immersed in sodium sulfate solution. Results of the experimental indicated that: the static compressive strength of specimens increases first and then decrease during corrosive period, the maximum growth rate is 12.71%, the final strength is only 82.84% and 90.22% of specimens which under normal environment and immersion in distilled water respectively; Similarly, the change regularity of longitudinal wave velocity increases first and then decrease, too, and the final velocity is only 87.95% and 91.41% of specimens which under normal environment and immersion in distilled water respectively; It was discovered that there are many crystals inside or around the pores after corrosion, and the crystals are ordered and arranged densely. So the highly salinity environment has a significant effect of weaken the mechanical performance of concrete.