This experiment was conducted to investigate the effects of dietary tryptophan levels on the production performance and egg quality of laying hens. Seven hundred and twenty 300-day-old ROM laying hens were randomly divided into five groups with three replicates per group and 48 laying hens per replicate. The diet of the control group was a basal corn-soybean meal diet containing 0.16% tryptophan. Through supplementing tryptophan into the basal diet, the tryptophan levels in diets of the experimental groups were 0.20%, 0.24%, 0.28% and 0.32%, respectively. The experiment lasted for 49 days. The results showed that the laying rate in 0.20% group was the highest of all groups and was increased by 2.18% (P<0.05), 3.08% (P<0.05), 3.23% (P<0.05) and 3.42% (P<0.05) compared with other experiment groups and the control group, respectively; there were no significant differences among the groups in average egg weight, average daily feed intake and feed-egg rate (P>0.05); compared with the control group, the albumen height and Haugh unit in 0.20% group were increased by 6.69% (P<0.05) and 2.20% (P<0.05); serum urea nitrogen contents in experiment groups were significantly reduced (P<0.05); serum total protein and albumin contents in 0.20% group were significantly higher than those in other groups (P<0.05); compared with the control group, serum FSH contents in 0.20% and 0.24% groups were increased by 14.69% (P<0.05) and 11.88% (P<0.05), and serum E2 contents were increased by 20.74% (P<0.05) and 15.56% (P<0.05), respectively. The results indicate that tryptophan can promote production performance of laying hens through enhancing gonadotropin release and protein availability, and the optimal tryptophan level in corn-soybean meal diet of laying hen is 0.20%. ［Chinese Journal of Animal Nutrition, 2010，22（5）:1265-1270］