Abstract: Taking four common green manure crops from different families and genera in Northern China as the test materials, and adopted a 2-year positioning improvement test method to study the changes in soil chemical properties of green manure crops at different growth stages, in order to provide reference for solving environmental problems caused by off-season vegetable cultivation.The results showed that there were differences in the changes in soil organic matter and nutrient content during the growth process of green manure.Compared to the first year, the organic matter content of green manure planting increased by 10.7% in the second year.Compared to basic soil fertility, planting and turning green manure significantly reduced the soil available phosphorus and nitrate nitrogen content, by 34.8% and 74.6%,respectively, and had a significant reduction effect on nitrogen and phosphorus accumulation in vegetable fields.There were also different in the effects of different varieties of green manure crops on soil nutrient content.The results of principal component analysis showed that the treatment of hairy leaved sweet potato had the greatest impact on soil nutrient content, followed by spring rapeseed treatment.