This experiment was conducted to evaluate the effects of vitamin A (VA) supplementation in diet on growth performance and immune function of laying hens and broilers. Two hundred and seventy female laying hens and 270 female broilers were assigned to 3 dietary treatments with 6 replicates (15 chickens per replicate), respectively. These laying hens and broilers received the same basal diet supplemented with 0, 4 000, 20 000 IU/kg VA, respectively. The feeding trial lasted for 84 days. Results showed as follows: the 0 IU/kg VA supplemental treatment had higher feed intake of laying hens and broilers than other treatments (P<0.05); VA supplemental levels had no significant effects on immune organ indices (thymus index, spleen index and index of bursa of Fabricius) (P>0.05); the 0 IU/kg VA supplemental treatment had higher heterophil to leukocyte ratio of laying hens and broilers than other treatments (P>0.05); the sheep red blood cell antibody titers and the Newcastle disease antibody titers of laying hens and broilers were increased with VA levels increasing; the keyhole lympet hemocyanin antibody titers, the concentrations of serum albumin and IL-2 of laying hens and broilers in the 4 000 IU/kg VA supplemental treatment were the highest. Immune organ indices and albumin concentration of the laying hens were significantly higher than those of broilers (P<0.05); there was no significant difference on the other immune indices between laying hens and broilers (P>0.05). The present study suggested that 4 000 IU/kg VA supplementation could improve growth performance and immune function of laying hens and broilers. When the supplemental level reached 20 000 IU/kg, it seemed to exert negative effects on growth performance and immune function. Immune indices between laying hens and broilers had not significant difference.［Chinese Journal of Animal Nutrition, 2010，22（4）:911-916］