Abstract: Objective: To explore the effects of tetraiodothyronine(T4) injecting into late-pregnant rabbit on pups growth.Methods:Ten rabbits which pregnant for 16 days were prepared and divided into two groups with equal number,of which test group and control group,0.3 mg T4 were injected intramuscular to pregnant rabbits of test group and 2ml 0.9% NaCl were injected to pregnant rabbits of control group respective.To observe the change level of hormone,estradiol (E2) of adult pregnant rabbit and change level of thyroxine,insulin and body mass of new born rabbit of two groups.Results:The levels of pregnancy rabbit plasma E2,T3 and T4 of test group were higher than the control group(P0.05 - P0.01).T3,T4 of 1 - 5 weeks after birth pups levels of test group were lower than the control group(P0.05 - P0.01).While in the 1,4,6 week,insulin levels were higher than the control group(P0.05 - P0.01),the test group treated pregnant rabbits T4 pups 1 - 6 weeks physique increase in weight were higher (P0.05 -P0.01).Conclusions:Late pregnancy rabbit with T4 treatment can improve new-born rabbits plasma insulin levels and increase the growth rate of them.