Grazing is one of the most important uses of desert grassland. Changes in livestock rates seriously affect the growth and development of plants. Endogenous plant hormones are the switches that regulate plant growth and development, and plants exhibit different physiologies at different stages of growth and development. In this study, the changes in endogenous hormones in the leaves of Stipa breviflora under different grazing conditions were studied to determine the response of Stipa breviflora to grazing, and the mechanism by which the number of tillers was affected by endogenous hormones were analyzed. The results showed that:(1) there was a significant quadratic correlation between endogenous hormones and stocking rates, suggesting that grazing significantly increased the concentration of endogenous hormones (P < 0.05), but this correlation existed only for medium and small strains of Stipa breviflora. (2) Grazing could affect the number of individual tillers of Stipa breviflora to a certain extent (P < 0.05), and heavy grazing had the most significant impact on the rate of individual tillers in Stipa breviflora. (3) The over-concentration of auxins (IAA) inhibited the number of tillers in Stipa breviflora (P < 0.01). However, no correlation was found between cytokinin (CTK) and the number of tillers of Stipa breviflora.