Abstract: The aim of this study was to investigate the effects of zymosan at different supplement dosages on production performance and immunity of hens. A total of 288 Liangfeng breeding hens at 45 weeks old were selected and assigned randomly into four treatment groups, three repeats in each group, 24 chicks in each repeat. The chicks in the group I , II, III and IV were fed with basal diet （Control）, basal diet supplemented zymosan at a level of 0.15%, basal diet supplemented zymosan at a level of 0.20%, and basal diet supplemented zymosan at a level of 0.25%. Prior the trial, the chicks had no significant different performance between groups. The prefeeding period was 1 week, and the experimental period was 7 weeks. The results showed that zymosan at different supplement dosages had significant effects on production performance and immunity of hens. When the zymosan was supplemented to the diets at a level of 0.15%,the laying rate, the fertility rate, hatchability, and level of IL-2 were increased by 4.56%, 3.27%, 7.45% and 7.54%, respectively. When the zymosan was supplemented to the diets at a level of 0.20%, the laying rate,the fertility rate, hatchability, level of IL-2 and level of IFN-γ were increased by 9.16%, 4.22%, 5.69%, 9.17% and 11.82%, respectively. Therefore, the optimal level of zymosan in hen diet is 0.20%.