[Objective] The response characteristics and demand changes of soil and microbial nutrients to shrub encroachment in Loess Plateau were investigated to provide reference for grassland resource management in the Loess Plateau. [Methods] The no-shrub encroachment grassland, subshrub (Artemisia sacrorum) encroachment grassland, and shrub (Caragana brachypoda) encroachment grassland in the Yunwu Mountain National Nature Reserve and measured the physicochemical properties of soil and activities of five enzymes involved in soil carbon, nitrogen, and phosphorus cycles. Afterward, we analyzed the effects of subshrub and shrub encroachment on soil nutrient content, enzyme activities, and stoichiometric ratios. [Results] Subshrub and shrub encroachment increased the content of soil water and nutrients and the activities of carbon, nitrogen, and phosphorus cycling enzymes. Soil microbial nutrient demands were not consistent across soil layers: in the 0—15 cm soil layer, soil microorganisms in the subshrub and shrub encroachment grassland had a higher demand for phosphorus element, whereas in the 15—30 cm soil layer, soil microorganisms had a higher demand for carbon element. Redundancy analysis showed that soil available nutrients were the key factors affecting soil enzyme activity and stoichiometric ratio. [Conclusion] Subshrub and shrub encroachment had positive effects on soil nutrient content and enzyme activity of enclosed grassland in Loess Plateau, and soil microorganisms under the subshrub and shrub encroachment grassland met their nutrient demands by changing the relative input of carbon, nitrogen, and phosphorus cycling enzymes; therefore, the trend of subshrub and shrub expansion in the region need to be further strengthened in the future. To maintain the stability of grassland ecosystem in Loess Plateau, corresponding regulatory measures need to be explored urgently.