Abstract: In order to investigate the effect of adding oregano oil in ration on beef quality in the aging process,ten Holstein bulls which had similar weight and age were employed in this experment.They were randomly divided into treatment group( added oregano oil) and control group( not added oregano oil),and were fed in the equivalent environment for eight months then slaughtered and measured their beef quality.The result showed that aging time and oregano oil had an interaction effect on the variation of beef color( p < 0.05).Before aging,the b*value and L*value of treatment group were significantly lower than that of control group( p < 0.05).On 7^th day,treatment group 's a*value was higher than that of control group( p < 0.10).In addition,the shear force,press loss,cooking loss of the treatment group were lower than that of the control group,while cooking percentage was higher than control group's during aging( p > 0.05).In the paper,adding oregano oil in ration can not only keep beef with fresh and red color for a long time,significantly reduce L*value and b*value,maintain stable p H,but also can improve beef tenderness,reduce press loss and cooking loss,finally improve cooking percentage and beef quality.