Abstract: OBJECTIVE To study the protection effects of eucalyptus on embryonic developmental toxicity in rats treated by cyclophosphamide. METHODS ①Twenty-five pregnant rats were randomly divided into 5 groups: three experiment groups (high, medium, low doses of eucalyptus group), negative control group (peanut oil group), positive control group (cyclophosphamide group). Three experiment groups and negative control group were administrated from the 10th to 14th day of gestation with eucalyptus in 100, 200, 300 mg·kg^-1·d^-1 and peanut oil 2 mL per animal per day respectively, while positive control group was ip with 12.5 mg·kg^-1·d^-1 cyclophosphamide at the 13th day of gestation. All pregnantrats 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. Another 25 pregnant rats were randomly divided into 5 groups like ①. Three experiment groups and negative control group pregnant rats were administrated from the 10th to 17th day of gestation with eucalyptus in doses like ①. All groups was ip with 12.5 mg·kg^-1 cyclophosphamide on the 13th day of gestation and sacrificed on the 19th day. Observed and noted target like ①. RESULTS ①After administration of eucalyptus (100, 200, 300 mg·kg^-1) for 5 days. The body, uterus, ovary and placenta weights of pregnant rats showed no significant difference compared with negative control group (P>0.05). The numbers for absorbed, live and dead fetus also showed no significant difference compared with negative control group (P>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 high doses of eucalyptus group’s fetus weight of body showed difference compared with negative control group (P<0.05), others had no significant difference (P>0.05). The fetus body weight, tail length in the positive control group were lower than those in the negative control group (P<0.05), but the fetus body length showed no significant difference compared with negative control group (P>0.05). ②Eucalyptus administration 8 days could dramatically decrease the rate of abnormal embryo and dead fetus induced by cyclophosphamide compared with the group without administration (P<0.05). CONCLUSION Under the experimental condition, eucalyptus showed no embryonic developmental toxicity, and it can restrain embryonic developmental toxicity in rats induced by cyclophosphamide.