Abstract: A comparison of rotational grazing and continuous grazing was conducted on Stipa breviflora desert steppe in the Sunit Right Banner of Inner Mongolia. The study on response of diurnal variation of photosynthetic characteristic of major plant species in different grazing system showed: 1) Double-peaks on the curves of diurnal changes of photosynthetic rates, transpiration rates and stomatal conductance of S. breviflora, Cleistogenes songorica and Allium polyrhizum, and there was a distinct phenomenon of “noon break”. There was a double-valley on the curves of diurnal changes of internal CO₂ concentration. 2) The different grazing regimes had no effect on the net photosynthetic rate or transpiration of the main plant species, but doubled the peak time in other the same conditions. 3) Rotational grazing and banning grazing increased stomatal conductance and internal CO₂ concentration of C. songorica.