Abstract: In order to study the quality change of Xinjiang brown cattle beef with different muscle fiber types during postmortem aging,eight representative parts of Xinjiang brown cattle was used,such as supraspinatus(SU),infraspinatus(IF),triceps brachii(TB),psoas major(PM),longissimus dorsi(LD),semitendinosus(ST),semimembranosus(SM)and biceps femoris(BF). During the aging process,the quality changes indexes were measured and analyzed at 1,6,12 h and 1,3,7,14 d,such as color difference,texture characteristics,shear stress,pressing loss,cooking loss,and pH value. It was found that The ST muscle of beef had the highest L^* value,and the PM had the highest a^* value. The hardness and elasticity of the eight parts increased first and then decreased with the aging time, and the hardness of the PM was lower than other parts. Eight parts of meat shear force as the aging time first increased then decreased,and the shear force of the PM was lower than other parts. For the change rate of shear force,the BF was the largest and the ST was the smallest. The water holding capacity of the PM was poor,but the SM was good. The cooking loss increased during postmortem aging. Eight parts of pH as the aging time first decreased then increased. The purpose of this study was to provide data support for the fine aging of Xinjiang brown cattle.