Nutrient content of the herbage on the rangeland is affected by growing period and decreased with changes of the growing season. The dynamics of nutrient content and digestibility of the mixed grasses and the sheep diet change under the different grazing systems. The study demonstrated that the nutrient content of the herbage on the rangeland was higher under grazing than it under no grazing. The nutrient content under rotate grazing (RG) was better than under continued grazing (CG) . The nutrient content of the sheep diet was higher than that on the natural rangeland (no grazing). The quality of the diet in RG was better than that in CG. The digestibility of the mixed grasses and the sheep diet correlate with the nutrient content positively and decrease with the changing seasons. The difference of digestibility among the different grazing systems was not obvious. The digestibility of the diet in CG was higher than that in RG before July, but opposite after July.