The cage–rearing Linwu ducks were used to study the effects of linoleic acid levels of 0.60%, 0.80%, 1.00%, 1.20% and 1.40% on laying performance, egg quality, serum biochemical indices and yolk fatty acid composition and then to estimate the linoleic acid for diets of the ducks during the peak laying period. The results showed that compared with the control group, dietary supplemented with different linoleic acid levels had no significant effect on the laying performance and egg quality of Linwu duck (P>0.05). The content of cholesterol and triglyceride in serum were decreased with the increasing of dietary linoleic acid level (P<0.05), and when dietary linoleic acid levels were 1.20 % and 1.40%, which were significantly lower than 0.60% linoleic acid group. The polyunsaturated fatty acids was increased with the increasing of dietary linoleic acid level (P<0.05), while the monounsaturated fatty acids of yolk was decreased(P<0.05). There were significant linear correlations between dietary linoleic acid level and the fatty acids composition of yolk palmitoleic acid, heptadecanoic acid, stearic acid, oleic acid, linoleic acid, artificial– linoleic acid and dicarbohexenoic acid. The results indicate that dietary 0.60% to 1.40% linoleic acid level had no adverse effect on laying performance and egg quality, but when linoleic acid level is 1.20% and 1.40%, the ducks can get better serum biochemical index and fatty acids composition of yolk.