Abstract: This experiment was conducted to study the effects of feeding different linseed level diets on performance, carcass characteristics and meat quality of lamb, and its mechanism. Thirty-two F1 lambs (two months old) of Suffolk sheep(♂)×Small-Tailed Han sheep(♀) were allocated into four groups with eight replicates in each group. Lambs were fed the diet with 0% (control group), 5%, 10% or 15% linseed (DM basis). The experiment lasted 60 days. All the diets were designed to contain similar contents of crude protein and digestible energy. The results showed that feeding diet containing 5% and 10% linseed could improve the performance, ADG（P<0.05） and carcass weight（P<0.05）of lambs, and decrease the ratio of Feed/Gain（P<0.01）. With the increasing of linseed content in the diet, water content of muscle was decreased （P<0.01） and the fat content in the muscle was increased（P<0.01）. The contents of total cholesterol, TG and free fatty acid in the blood tended to increase（P>0.05）. The activity of lipase decreased. The diet containing 5% to 15% linseed significantly modified meat quality of lamb. Linseed improved cooking percentage, intramuscular fat and MFI （P<0.01）of muscle, so it improved the muscle tenderness. Linseed in diet declined the oxidation resistance, but had no effect on the meat color(P>0.05). Linseed supplement improved the fatty acid profile, especially increased the amounts of PUFA（P<0.01）, CLA（P<0.01）, linolenic acid（P<0.01） and the ratio of n-6 to n-3 PUFA（P<0.01）. Diet containing 5% to 10% linseed could increase growth performance and improve the meat quality through optimizing fatty acid profile and increasing PUFA content, especially CLA content of meat.