Seasonal dynamics of soil catalase(CAT),peroxidase(PEX),polyphenol oxidase(POX),protease(PRO),invertase(INT) and alkali phosphotase(ALP) activities in west Songnen alkali degraded grassland are examined.The results indicate that the changing patterns of PEX,PRO,INT activities vary from season to season,while CAT,POX,ALP activities bear the same changing tendency and their peak value appears in August or September in alkali spot,severe,moderate and mild degraded soils.Enzymatic activities of different seasons have the various ranges in different degraded types of soil.Changing ranges of CAT,POX and ALP in moderate and severe salinization soil are more than that in mild soil.However,changing ranges of PEX,PRO and INT activities in moderate and severe salinization soils are less than that in mild soil.There is seasonal relevance between different enzymatic activities,but they are different in different types of soil.