In this study, four grassland types distributed along the altitude were selected in the typical arid area of Xinjiang, and the effects of shrub on the chemical structure and thermal stability of grassland soil organic carbon (SOC) were revealed by using solid-state ¹³C nuclear magnetic resonance technology and thermal analysis technology. The results show that the proportion of aromatic C among shrubs is decreased gradually from temperate desert to mountain meadow along the altitude. In temperate desert, temperate grassland desertification, temperate desert grassland and mountain meadow, the alkyl C/O-alkyl C values under shrubs are increased by 0.10, 0.09, 0.03 and 0.21 respectively. The index of low altitude temperate desert and temperate grassland desertification, the ratio of the mass of SOC easily decomposed by heat (SOC decomposed at lower temperature) to the total mass of SOC (%Exo₁), the temperature at half of SOC decomposition (TG-T₅₀) and the corresponding temperature at half of SOC energy release (DSC-T₅₀) are significantly lower than those of high-altitude temperate desert grassland and mountain meadow. In grassland desertification, desert grassland and mountain meadow, the %Exo₁ and DSC-T₅₀ under shrub are higher than those between shrubs, while TG-T₅₀ is lower than that between shrubs. In temperate desert, from shrub to shrub, the proportion of energy released by SOC combustion in total combustion energy (Q) is decreased at low temperature, while the energy released by SOC combustion is increased at high temperature. The results show that shrub can increase the stability of SOC chemical structure and thermal stability in arid area.