Abstract:Grassland ecosystem is one of the most important components of terrestrial ecosystem. Grassland resources are the basis for herdsmen to survive, in recent years with the increase of population in pastoral areas and the over-exploitation and utilization of grassland, the grassland ecosystem has been seriously damaged. In this paper, the contents of C, N and P in the overground and underground parts of Stipa krylovii population and soil under different grazing intensities were studied in desert grassland of Inner Mongolia. The results showed that the species diversity of desert grassland was significantly higher than that of moderate and heavy grazing (P < 0.05). With the increase of grazing intensity, The content of C, N, C:N, N:P, C:P in the soil increases first and then decreases, and the content of P in the soil increases with the increase of grazing intensity. With the increase of grazing intensity, the content of C in the aboveground part of Stipa krylovii decreased, and N, P, N:P increased first and then decreased, while C:P decreased first and then increased. The contents of C, N, N:P in the underground part of Stipa krylovii have been increasing. P content first decreased and then increased, while C:N, C:P were contrary to the rule of p content. Compared with the contents of elements in the overground part, The correlation between the content and ratio in the underground part of Stipa krylovii and the contents of elements in the soil is higher, which indicates that the root system of dominant plants in the desert grassland and its soil environment have certain cooperative change ability under grazing conditions.