Exopalaemon carinicauda is an economically important shrimp species that is naturally distributed in the estuaries and coastal areas of China, especially in the Yellow Sea and the Bohai Sea, and contributes to one-third of the gross output of polyculture ponds in eastern China. Despite its economic importance, basic biological knowledge about this species remains limited. Salinity is one of the most important and changeable water quality factors affecting the physiology of aquatic organisms. Salinity variation may cause a variety of physiological responses, such as plasma enhanced stress-related hormones, stimulation of energy metabolism, and disruption of electrolyte equilibrium. Consequently, marine organisms have developed various survival mechanisms against salinity variation. For example, crustaceans adjust osmolarity and maintain an intra-corporal stable state by varying related enzyme activities. E. carinicauda live in estuaries and coastal areas with highly variable salinity; yet, little is known about the osmotic adjustment mechanisms of this species. Enzyme activity regulation is one of the most important osmotic adjustment mechanisms. To investigate the effects of acute and gradual salinity changes on enzyme the enzyme activity of E. carinicauda, two different experiments (acute change and gradual change) were performed. In the gradual change experiment, we used two different treatments. In the first treatment, the salinity was gradually raised from 33 to 40 and 45. In the second treatment, the salinity was gradually reduced from 33 to 5, 10, 15, 20, 25, and 30. For each salinity level, a group of 45 animals were randomly selected and cultured for two weeks. In the acute change experiment, five groups of 45 animals were randomly selected at 33 salinity, which was then abruptly changed to 0, 5, 15, 25, and 45. In each group, blood was collected from the animals for further enzyme activity analysis. ATPase (Na⁺/K⁺-ATPase and total ATPase), alkaline phosphatase (AKP), acidic phosphatase (ACP), and superoxide dismutase (SOD) activity was detected. In the gradual change experiment, maximum ATPase activity occurred at salinity 5. Interestingly, at the start of increasing salinity, ATPase activity rapidly decreased, but then increased with increasing salinity. Total ATPase activity was more stable in the range of salinity changes between 15 and 30, and reached a minimum level within this range. However, AKP and ACP activity was not significantly affected by gradual salinity changes. SOD activity initially increased, but then decreased with increasing salinity, with the maximum being detected at salinity 33. In the acute salinity changes experiment, ATPase activity fluctuated more intensely than AKP and SOD activity, while ACP activity was minimally affected. The results indicate that the effects of acute change on related enzyme activity were greater than those obtained through gradual change. ATPase and SOD activity was more vulnerable to salinity change than AKP and ACP activity. Overall, osmotic adjustment and immune related enzyme activity are very sensitive to salinity changes. These results are expected to help improve our understanding about the mechanisms of osmotic, metabolic, and immune regulation of E. carinicauda responses to salinity changes. Which are expected to set a foundation for future breeding and resource protection for this species.