In order to investigate the effects of Macleaya cordata extract on growth performance, organ index, serum biochemical index and immune function of squabs, the trial had adopted one-factor completely random design. A total of 280 healthy ten-day-old squabs with similar weight were randomly divided into 7 groups with 10 replicates per group and 4 squabs per replicate. The control group (group A) was fed a basal diet, and the experimental groups (groups B to G) were fed diets added 30, 40 and 50 mg/kg of Macleaya powder, 40 mg/kg Macleaya cordata extract PE50, 40 mg/kg Macleaya cordata extract BE60 and 150 mg/kg chlortetracycline, respectively. The experiment lasted for 15 days after pre trial period of 5 days. The results showed as follows: 1) no significant differences were found in average daily weight gain and feed to gain among all groups (P>0.05). 2) No significant differences were found in thymus index and bursa index among all groups (P>0.05). The spleen index of group E was significantly higher than that of control group (P<0.01), and the spleen index of group D was significantly higher than that of control group (P<0.05). The pancreas index of group D was significantly higher than that of control group, group B and group F (P<0.05). 3) Serum total protein content of group E was significantly higher than that of group G (P<0.01). Serum low density lipoprotein content of group B was significantly higher than that of control group (P<0.05). 4) Serum immunoglobulin G content of group D was significantly higher than that of control group and group B (P<0.01), and was higher than that of other groups (P<0.05). Serum interleukin 6 content of group E was significantly lower than that of control group (P<0.05). The results indicate that Macleaya cordata extract can increase the immune organ index and the content of total protein, low density lipoprotein and immunoglobulin G in serum, thereby enhancing immunity of squabs.