In this study, 192 one-day-old Aiba Yijia(AA) broilers were randomly and equally divided into four groups including a control group fed with basic diet and three experimental groups fed with a diet supplemented with 400, 800 and 1200 mg/kg mulberry leaf extract. At the two stages of 1-21-days-old and 22-42-days-old, the growth performance, serum antioxidant indexes, physiological and biochemical indexes related to fat metabolism, meat color, pH value, drip loss rate, crude fat content and fatty acid composition of AA broilers were measured respectively to investigate the effect of mulberry leaf extract on the meat quality of AA Broilers and its mechanism how the extract affect the meat quality. The results showed that compared with the control, the leaf extract treatments had no significant effect on the daily feed intake, feed to weight ratio, average daily gain, body weight and muscle pH of AA broilers; while could extremely significantly or significantly reduce the crude fat content and the proportion of total saturated fatty acids of breast muscle, and the crude fat content of leg muscle of 42-days-old broilers; and significantly or extremely significantly increase the proportions of eicosadienoic acid, eicosatrienoic acid, eicosatetraenoic acid, docosahexaenoic acid, total polyunsaturated fatty acids of breast muscle of 42-days-old broilers and the activities of glutathione peroxidase(GSH-PX) and catalase(CAT) in serum of 21-days-old broilers. The diet supplemented with 800 mg/kg mulberry leaf extract could significantly or extremely significantly reduce the 24-hour drip loss rate and the proportion of 24-carbonic acid in the breast muscle of 42-days-old broilers, and the crude fat content in the leg muscle and breast muscle and the total cholesterol(TC) concentration in the serum of 21-days-old broilers; and extremely significantly improve the redness of the leg muscle, the proportion of palmitoleic acid in the breast muscle and the CAT activity in the serum of 42-days-old broilers. The diet supplemented with 1200 mg/kg mulberry leaf extract could also significantly or extremely significantly reduce the 24-hour drip loss rate of the leg muscle of 21-days-old broilers and the breast muscle of 42-days-old broilers, the crude fat contents of breast and leg muscle and the serum MDA content of 21-days-old broilers, as well as the proportions of palmitic acid and 24-carbonic acid of the breast muscle and the serum TC concentration of 42-days-old broilers; significantly or extremely significantly improve the serum T-AOC of 21-days-old broilers, and the redness of leg muscle and the yellowness and the proportions of palmitoleic acid, oleic acid and total monounsaturated fatty acid of breast muscle, and the serum CAT activity and HDL-C concentration of 42-days-old broilers. Taken together, by using the way, reducing the fat to improve meat quality, it was favor of adding mulberry leaf extract at a dosage of no less than 800 mg/kg.