Objective To study the effects of eucalyptus on embryonic development of rats. Methods Totally 25 pregnant SD rats were randomly divided into 5 groups, each had 5 rats: three experiment groups ( high，medium，low doses of eucalyptus), negative control group ( peanut oil), positive control group (cyclophosphamide). Three experiment groups and negative control group were lavaged from gestation 10 to 14 days with eucalyptus in 100mg/(kgI>&#/I>8226;d), 200mg/(kgI>&#/I>8226;d), 300mg/(kgI>&#/I>8226;d) and peanut oil 2ml per animal per day respectively, while positive control group was ip with 12.5mg/(kgI>&#/I>8226;d) cyclophosphamide at gestation 13 days.All pregnant rats were sacrificed at the 19th day. The body, uterus, ovary and placenta weights of the pregnant rats were measured respectively. The numbers of absorbed, live and dead fetus were counted, respectively. The length for fetus body and tail as well as body weights were measured. Results After administration of eucalyptus (100mg/kg,200mg/kg,300mg/kg) for 5 days, the body, uterus, ovary and placenta weights of pregnant rats showed no significant difference compared with negative control group(EM>P/EM>>0.05).The numbers for absorbed, live and dead fetus also showed no significant difference compared with negative control group ( EM>P/EM>>0.05 ). All of the fetus body weights, body length and tail length were larger in the treated groups than those in the negative control group. But only in high doses of eucalyptus groups, the fetus weight of body showed difference compared with negative control group (EM>P /EM><0.05), others had no significant difference (EM>P/EM>> 0.05). The fetus body weight, tail length in the positive control group were lower than those in the negative control group (EM>P/EM> <0.05),but the fetus body length showed no significant difference compared with negative control group (EM>P /EM>>0.05). Conclusion Under the experimental condition, eucalyptus showed no embryonic developmental toxicity, where cyclophosphamide showed embryonic developmental toxicity.