Abstract: An experiment was conducted using a total of 288 day-old Arbor Acres male broilers to study the effect of supplemental t-10, c-12 CLA levels on growth performance, carcass traits, and abdominal fat of the broilers. Birds were randomly allotted by body weight to one of six treatments in a completely randomized design. They were fed either a CLA-unsupplemented corn-soybean meal basal diet or fed basal diets supplemented with 0.20, 0.40, 0.60, 0.80 or 1.00 % t-10, c-12 CLA for duration of 42 days. The result shows that the supplemental CLA had no effect (P＞0.05) on the ADFI, percentage of breast and leg muscles，but affected abdominal fat percentage (P< 0.001 ), ADG and F/G(P<0.05). The addition of 0.20, 0.40, 0.60, 0.80 or 1.00 % CLA resulted in a decrease in abdominal fat percentage (P<0.01), and broilers fed on the 0.60% t-10, c-12 CLA had a higher ADG and F/G (P<0.05). The addition of 0.20, 0.40, 0.60 or 1.00% CLA decreased b* value and shear force in the breast muscle (P<0.05), but not in the thigh muscle. The addition of CLA significantly increased taste estimate in breast muscle. The addition of 0.20, 0.40, 0.60 or 1.00% CLA increased MDH activity in abdominal fat, but decreased MDH activity in other tissues and serum leptin (P<0.01).Results from this study indicate that the addition of t-10, c-12 CLA to broiler diets might increase growth performance and feed conversion, decrease the percentage of abdominal fat by decreasing MDH activity in abdominal fat and leptin in serum, increasing MDH activity in liver, breast and thigh muscle.