This experiment was conducted to study the effects of dietary lysine (Lys) level on performance, egg quality, serum biochemical indices and nitrogen metabolism of Linwu ducks in peak laying period (30 to 38 weeks of age), and to evaluate Lys requirement of Linwu ducks during the peak laying period. A total of 200 healthy Linwu ducks with nearly same body weight and laying rate (P>0.05) were randomly assigned to 5 groups with 5 replicates in each group and 8 ducks in each replicate, and fed basal diet supplemented with 0.65%, 0.75%, 0.85%, 0.95% and 1.05% Lys for 63 days, respectively. Ten ducks per group were picked up on the basis of individual weight immediate to the average weight of every group at the end of the feeding experiment, and the ducks were used in metabolism experiment. The results showed as follows:1) The daily egg weight in 0.95% and 1.05% Lys groups was significantly higher than that in 0.65% and 0.75% Lys groups (P<0.05), but the feed/egg in 0.95% and 1.05% Lys groups was significantly lower than that in 0.65% and 0.75% Lys groups (P<0.05). 2) Dietary Lys level had no significant effects on egg quality of laying ducks (P>0.05). 3) The serum total protein content in 0.85%, 0.95% and 1.05% Lys groups was significantly higher than that in 0.65% Lys group (P<0.05). The serum triiodothyronine content in 0.95% Lys group was significantly higher than that in 0.65%, 0.75% and 1.05% Lys groups (P<0.05). 4) Compared with 0.65% Lys group,the net protein utilization (NPU) and nitrogen deposition in 0.95% Lys groups were significantly improved (P<0.05 or P<0.01). 5) According to the quadratic regression analysis based on total protein, NPU and nitrogen deposition, the optimal dietary Lys levels for Linwu ducks were 0.92%, 0.96% and 0.95%, respectively. In conclusion, the daily egg weight, feed/egg, total protein, NPU and nitrogen deposition of Linwu ducks aged from 30 to 38 weeks are more sensitive to changes of dietary Lys level. The optimal dietary levels in diet of Lys for Linwu ducks is 0.92% to 0.96%, that can obtain the best performance, serum biochemical indices and nitrogen metabolism.