Abstract: In order to analyze the effects of the changes in the nutrient composition of the grass population on the weight gain and reproductive performance of different weaning ewes in the temperate desert steppe of Xinjiang pastoral area, the grazing multiparous Suffolk sheep, Suffolk sheep and Chinese Merino sheep（Xinjiang Army Reclamation Type） were selected as the research objects. The weight of weaning ewes, forage yield and nutrient composition of the grass population（crude protein, crude fiber, crude fat, crude ash, calcium, phosphorus, nitrogen free extract, etc.） were measured regularly from June to September. The litter size of ewes, litter weight at birth and weaning weight of lambs were recorded, and the relationship between the yield and nutrient composition of forage and the weight and reproduction of ewes was analyzed. The results showed that the temperature in Xinjiang pastoral area was higher and the number of rainfall days decreased from June to August, and the temperature dropped and the number of rainy days increased in September. From June to September, the forage yield, dry matter, crude ash, crude fat and crude fiber content of Festuca arundinacea, Stipa arundinacea and Seriphidium sericicum decreased first and then increased in the warm desert steppe of Xinjiang pastoral area. The weight of multiparous Suffolk sheep, Suffolk sheep and Chinese Merino sheep（Xinjiang military reclamation type） decreased from 63.50 kg, 91.33 kg, 56.25 kg to 63.33 kg, 86.00 kg, 51.50 kg, and the weight of the three breeds decreased by 0.27%, 5.84% and 8.44% respectively. The litter size of multiparous Suffolk ewes that did not recover to the initial weight and that recovered to the initial weight were 1.83 and 1.91, respectively, and that of Suffolk sheep were 0.93 and 1.00, that of Chinese Merino sheep were 0.95 and 1.00, respectively, There was no significant difference among groups in the same variety（P＞0.05）. The litter weight at birth and weaning weight of lambs from multiparous Suffolk sheep, Suffolk sheep and Chinese Merino sheep that did not recover to the initial weight were significantly lower than those of lambs in ewes that returned to the initial weight（P＜0.05）. The results indicated that with the continuous increase of temperature and the decrease of rainfall from June to August, the yield of Festuca arundinacea, Stipa arundinacea and Seriphia sericea type grass groups showed a downward trend in the temperate desert steppe in Xinjiang pastoral area. With the decrease of temperature in September, the forage yield increased. The multiparous Suffolk ewes had strong grazing adaptability, and the maintenance ability to weight（fat） was better than that of Suffolk sheep and Chinese Merino sheep.