Abstract: Aim: To determine the efficacy and the safety of different dosage of Mifepristone and misoprostol as induc-tion agent for initiation of laber at term. Methods: 150 pregnant women at term who had clear clinical indications for labor in-duction but had unfavorable cerivices (Bishop5) were randomly assigned to A, B, C groups. Each group contained 50 cas-es, In group A all women took 200mg of Mifepristone on days l of 2 - day observation Period; 100mg of Mifepristone in group B and no tablelet in group C. 48 hours Iater 50μg of Misopristol was placed in the opterior vaginal fonix every 3 hours with a potential maximum of 4 doses. Result: 44 % of cases in group A and B had mature cervices (Bishop m inereed3) but only l2% of cases in group C had such increas (P 0.01 ). 25 cases entered spontaneous labor without using Misoprostol.13 in group A, 10 in group B and 2 in group C (P0.05). There was a significant difference in the bo of Misoprostol re-quirement between the group A, B and the group C. In group A, B 1 ~ 2 doses Misoprostol requirement accounted for 78.4% and 77. 5 % of cases respectively, versus 56. 25 % of cas in group C while 3 ~ 4 doses Mboprostol need is 10. 8% and 12. 5 % of cases in group A, B versus31. 3 % cases in group C (P 0.05). There was a higher prevalenee of meconium passage in group C (28%, P 0.05). Among 3 groups the observation of pathomorPhology of placenta and decidua show no speific lesion. Conlusion: ①Administration of loomg of Mifepristone, 48 - hour before induction of labor can improve the Bishop score of un favorable cervices of the women at term and reduce the doese of Misoprostol, which is gdri for high risk pregnancy. ②Low - dosage of Mifepristone seerns not making obvious patholOgicaI lesion in term placenta and decidua, and therefore, it has proved safe in the cases.