Red sand ridge is a special desertification landscape formed by land degradation of red beds landforms. Soil microorganisms can be an evaluation soil quality indicator. In this study，a field experiment was conducted to determine the effects of various soil ameliorations and their combined modes on the microbial diversity and community structure of degraded soil in red sand ridge，which provided the theoretical and technical foundation to formulate methods for ameliorations incorporation and sustainable utilization of soil. Combining three improvements including microbial inoculant，straw mulching and vermicompost，eight treatments were carried out in this experiment:(1)microbial inoculant + organic fertilizer + straw mulching，(2)microbial inoculant + organic fertilizer，(3)organic fertilizer + straw mulching，(4)microbial inoculant + straw mulching，(5)straw mulching，(6)microbial inoculant，(7)organic fertilizer，(8)control treatment. The relationship between soil physicochemical properties and microbial community characteristics and the impacts of three improvements and their combined modes on them were analyzed. The results showed the improvement effect of the stalk mulching treatment on soil microbial diversity and community structure was significantly higher than that of the control treatment，while the effects of vermicompost and bacterial agents were limited. However，compared with single improvement measures，the combination of them significantly increased the total soil microbial biomass and the biomass of various groups，and significantly improved soil microbial diversity and community structure without exception. In addition，compared with the control treatment，the relative abundance of fungi，arbuscular fungi and gram-negative bacteria was significantly increased by the combination of various improvement measures and mulching treatment，and the relative abundance of gram-positive bacteria and anaerobic bacteria was decreased. Correlation analysis showed that soil microbial diversity and biomass were significantly positively correlated with soil moisture content，organic carbon，alkali-hydrolyzable nitrogen，available potassium，and available phosphorus，and were significantly negatively correlated with pH. Redundancy analysis showed that changes in soil microbial composition were mainly affected by moisture content，pH，soil organic matter，available potassium，alkali-hydrolyzable nitrogen，and available phosphorus content. In summary，the comprehensive effect of straw mulching combined with organic fertilizer and microbial inoculant could effectively regulate the ecological environment of degraded soil in red sand ridge and significantly increase soil microbial biomass and optimize microbial community structure.