Abstract: In order to provide theoretical basis for evaluating the quality of the Yongchang sheep,the Yongchang sheep fed with Agaricus bisporus stalk and Gannan Tibetan sheep were studied and analysis for the quality of mutton after being fed for 8 months,such as the surface brightness value,the cooked meat rate and the protein content. The results showed:the surface brightness value of L^* in Yongchang mushroom sheep is 32.27,and the cooked meat rate is 67.51%,the pH is 5.86,the water content is 75.88 g/100 g,the protein content is 21.37 g/100 g,the water loss is 28.17%,the shear stress is 5.31 kg/cm²,the fat content is 2.01 g/100 g,and rich in amino acids and fatty acids. The surface brightness value of L^* in Gannan Tibetan sheep is 30.72,and the cooked meat rate is 60.41%,the pH is 5.57,the water content is 71.01 g/100 g,the protein content is 20.06 g/100 g,the water loss is 33.21%,the shear stress is 6.14 kg/cm²,the content of fat is 2.31 g/100 g. Compared with Gannan Tibetan sheep,the mutton from Yongchang sheep fed with mushroom stalk had higher protein,lower fat,better tenderness and higher nutritional value.