To explore the fertilization effect and soil improvement effect of organic fertilizer and straw mulching on saline-alkali farmland soil，the typical saline soil in Hetao irrigation district was taken as the research object.The effects of no fertilization(CK)，chemical fertilizer(CF)，chemical fertilizer + organic fertilizer(CFM)and chemical fertilizer + straw mulching(CFS)on soil pH，organic carbon and total nitrogen content，available nitrogen，phosphorus and potassium content and microbial quantity were compared and analyzed.The correlation between soil chemical properties and soil microbial quantity in shallow(0～20 cm)under nitrogen conditions was studied by simple correlation analysis and redundant analysis，and the driving factors of soil microbial quantity difference under different fertilization measures were revealed.The change characteristics of soil fertility under the two main fertilization measures of organic fertilizer and straw mulching were clarified.The results showed that compared with CK，soil pH decreased by 1.36%～1.78% and 1.02%～1.44% under CFM and CFS treatments，respectively.Organic fertilizer and straw returning slowed down the trend of soil salinization.CFM and CFS treatments increased soil organic carbon and total nitrogen content，and significantly increased soil available nitrogen，available phosphorus and available potassium content，and the effects of organic fertilizer were better than those of straw returning.In terms of soil microorganisms，CFM significantly increased the number of soil bacteria(53.44%～59.78%)and actinomycetes(10.08%～16.79%)，and CFS significantly increased the number of soil fungi(29.99%～49.06%).In summary，organic fertilizer application and straw returning reduced soil pH，increased soil organic carbon and nutrient content，increased the number of soil microorganisms，and improved soil microenvironment. The results of this study can provide reference for soil improvement and fertilization of saline soil in river-loop irrigation district.