[Objective] For the purpose of finding a well-behaved soil improvement method in degraded drought mountain lands, the influences of different soil and water conversation measures on soil physical and chemical properties were illustrated. [Methods] Coneventional planting(contrast) and combined mulching treatments of water retention agent, maize straw and plastic film were designed in a newly planted walnut orchard in the drought gneiss area in Hebei Taihang Mountain in order to research their effects on soil nutrients and microorganisms. [Results] Soil nutrient content and microorganism population increased significantly under straw mulch as compared with the contrast. Amounts of soil bacteria and actinomycetes, soil organic matter content, soil total N, total P, total K, effective P and available K increased by 14.04%,17.42%,25.53%,60.29%,25.90%,15.31%,143.67% and 51.44% respectively. Soil nutrient content and microorganism population declined slightly under water retention agent treatment. As compared with the contrast, the quantities of soil bacteria, fungi, actinomycetes, cellulose decomposing bacteria and the contents of soil organic matter, total N, total P decreased under plastic film mulching decreased by 27.19%, 21.0%, 10.11%, 31.07%, 1.11%, 22.06% and 6.06%; the contents of total K, effective P and available K, increased by 12.6%, 9.65% and 8.09%, respectively. The effects of combined treatments on soil nutrient contents and microorganism population were differently greatly. The most effective treatment on soil nutrients and soil microorganism amounts was not the combined treatment of water retention agent, straw and plastic film were as expected. The best measure was the combined mulching of water retention agent and maize straw. As compared with the contrast, the quantities of soil bacteria and actinomycetes, and the contents of soil organic matter, total N, total P, total K, effective P and available K, increased by 16.67%, 3.37%, 6.63%, 92.64%, 12.67%, 1.8%,94.25%, and 105.76%, respectively. [Conclusion] Soil nutrient and microorganism population closely interacted with soil moisture, heat, air condition. Soil and water conversation measures can change moisture, heat, and air condition of soil. Through this, mulching can indirectly change soil nutrient and microorganism population.