Objective To explore the effect of lanthanum nitrate on immunity in rats. Methods One hundred and sixty SPF weaned rats were randomly divided into two batches, 80 rats in each group and randomly divided into control, low, medium and high dose group, with 20 rats (male and female) in each group.On the 24th day after birth, lanthanum nitrate solution was administered at doses of 0,2, 20 and 60 mg/kg BW respectively. On the 51st day after birth, the first batch of rats were tested for main organs, organ-body ratio, peripheral blood lymphocyte type and serum cytokines; splenic T and B lymphocyte proliferation and splenic antibody-producing cells were measured on the 54th day after birth to the second batch of rats. Results There was no significant difference of body weight among the three dose groups and the control group to the two batch of rats (P>0.05). The absolute and relative weight of kidney and viscera of male rats in middle and high dose groups were significantly higher than those in control group (P<0.05). The brain weight and viscera ratio of female rats in low dose group were higher than those in control group (P<0.05). The number of natural killer cells in the high dose group was significantly lower than that in the control group, with dose-response relationship (P<0.05).The ratio of CD4/CD8 in the low dose group was significantly higher (P<0.05). The number of T cells in the low dose group was significantly higher(P<0.05), however the number of B cells in the low dose group was significantly lower(P<0.05). Based on the immunotoxicity test parameter. Conclusion In this experiment, lanthanum nitrate had immunotoxic effects on rats, based on the immunotoxicity test parameter, the baseline lower limit value of immunotoxicity was 8.10 mg/kg BW.