In order to explore the improvement effect of compound microbial fertilizer on alkaline soil，a field test of applying compound microbial fertilizer on the alkaline soil was carried out at the test site of Hailiutu Science and Technology Park，Inner Mongolia Agricultural University，and its effects on soil biological characteristics and soil fertility were discussed. The results showed that the application of the compound microbial fertilizer treatment significantly reduced the pH and EC values of the ploughed layer soil，which decreased by 0.32～0.88 units and 0.17～0.39 mS/cm，respectively. The soil enzyme activity，microbial carbon and nitrogen，organic matter，and fast-acting nutrient content were significantly improved. Catalase，urease，phosphatase active enzyme and sucrase activity increased by 62.90%～158.06%，57.66%～74.82%，38.89%～69.44% and 41.37%～53.25%. Soil microbial carbon，nitrogen，carbon-nitrogen ratio and microbial entropy increased by 71.41%～82.36%，29.13%～31.84%，30.16%～37.13% and 33.33%～37.68%，respectively. Soil organic matter，alkaline nitrogen，available phosphorus and available potassium content increased by 22.48%～35.19%，22.40%～33.33%，104.04%～132.97% and 34.28%～37.82%. Compared with the conventional fertilization treatment，the application of compound microbial fertilizer treatment reduced the pH and EC values of the cultivated layer soil by 0.16～0.72 units and 0.06～0.28 mS/cm，respectively；significantly increased soil enzyme activity，microbial carbon and nitrogen，organic matter，and available potassium content；Soil urease，phosphatase active enzyme and sucrase activity increased by 15.82%～28.42%，21.95%～48.78% and 29.32%～40.19%，respectively；soil microbial carbon，nitrogen，carbon-nitrogen ratio and microbial entropy increased by 37.07%～45.82%，15.79%～18.22%，26.27%～33.03% and 21.05%～25%；soil organic matter and available potassium content increased by 10.40%～21.85% and 23.66%～41.19%，respectively. The above results show that the application of composite microbial fertilizer can obviously improve the biological properties of alkaline soil and soil fertility.Among different gradients of fertilizer application，the comprehensive effect of 1500 kg/hm² treatment is the best.