The Oncorhynchus masou was cultured in four salinities groups, 0, 8‰, 16‰, 24‰(denoted as CK, S1, S2 and S3) for 42 d, respectively. The blood biochemical indicators of the tail vein blood and the digestive enzyme activities of the stomach, pyloric caecum, intestinal tissues were measured. These results showed that the osmotic pressure, Na+ and Cl- concentrations increased, while the total protein mass concentration increased first and then decreased with the increasing of salinity, and the difference among these salinity groups had a statistically significant(P＜0.05). The blood glucose levels in S1, S2 groups were significantly higher than those of the CK, S3 groups(P＜0.05), and the high density lipoprotein and low density lipoprotein concentration of S1 group were the highest. The activities of γ-glutamyl transpeptidase and lactate dehydrogenase in serum enzymes decreased, while the activities of aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase increased first and then decreased with the increase of salinity. The urea nitrogen in serum metabolites had no significant difference between these groups(P＞0.05), however the creatinine concentration was decreased with the increase of salinity, and the uric acid concentration increased first and then decreased with the increase of salinity. In addition to the pepsin activity in pyloric caecum of the S2 group, the trypsin and pepsin activities were decreased in the stomach, pyloric caecum and intestinal tissues of Oncorhynchus masou with the increase of salinity and there was significant difference between S3 and CK groups(P＜0.05), while there were no changes of lipase and amylase activities in all groups. By adjusting its own functions to better adapt to the changes of salinity, the blood biochemical indexes of Oncorhynchus masou had changed under different salinity conditions, while the changes of digestive enzyme activity could reveal the complexity and tissue specificity of their functions.