Abstract: The non-specific immune functions were studied in four populations of Portunus trituberculatus from Haizhou Bay, Dandong, Zhoushan and Laizhou Bay for the immunity enzyme activities in haemolymph, muscle and hepatopancreas tissue of the crabs. Results showed that SOD activities of haemolymph and muscle were not significant different by four populations. However, the hepatopancreas SOD activity of Haizhou Bay population was higher than that of Laizhou Bay population significantly (P<0.05), and there was no significant difference among other populations (P>0.05). On the GSH-px activities of the haemolymph and hepatopancreas, Haizhou Bay population was significantly higher than Laizhou Bay population (P<0.05). The MDA content, LSZ and ALP activities in different tissues were similar and there were no significant differences among the four populations. The results of the immunity enzyme activities are quite correlated with those of nonspecific immunity abilities of preventing disease and disease resistance evaluation.