Abstract: Contents of nitrate and nitrite in leafy vegetable and in vegetable soil as affected by combined applications of organic and chemical fertilizers were determined through plot experiment and laboratory analysis.The results show that the combined application of chemical and organic fertilizers decreased the contents of nitrate in the vegetable and the soil,and reduced downward leaching of nitrate in the soil significantly.Especially when the ratio of organic manure and chemical fertilizer was 1∶1 much better effects could be observed,such as higher yield of Chinese cabbage,and lower nitrate concentration in the vegetable and in the subsoil of the vegetable field.