Abstract: The effects of five different fertilization measures（no fertilization（CK）,combined application of nitrogen and phosphorus fertilizer（NP）,combined application of nitrogen, phosphorus and potassium fertilizer（NPK）,single application of organic fertilizer（M） and combined application of organic fertilizer and nitrogen and phosphorus fertilizer（MNP）） on soil enzyme activity and soil fertility were studied by field experiment with different fertilization soils as test materials, in order to solve the rational application of organic fertilizer in agricultural production in loess hilly area, reduce the amount of chemical fertilizer, improve the soil ecological environment, and provide reference for the sustainable development of agriculture.The results showed that fertilization significantly increased the soil nutrient content from 0 to 20 cm, and the soil fertility was more significantly increased under the treatment of organic fertilizer.In addition to soil water content, the nutrient content of soil 20-40 cm under different fertilization treatments was significantly lower than that of soil 0-20 cm.Fertilization significantly increased soil enzyme activity from 0 to 20 cm, and the highest enzyme activity was found under MNP treatment.Fertilization treatment had different effects on the enzyme activity of 20-40cm soil,and the enzyme activity of 20-40cm soil was significantly lower than that of 0-20cm soil under different fertilization treatment.The application of organic fertilizer,especially the application of organic fertilizer combined with chemical fertilizer,could improve soil internal ecological environment,soil nutrient cycling capacity and soil enzyme activity,and should be one of the important measures for farmland production in loess hilly area.