Objective To evaluate the effectiveness of mifepristone concomitant with misoprostol for medical abortion. Methods We searched the related original studies worldwide, and controlled prospective studies and systematic reviews based on randomized controlled trials （RCTs）. Nine electronic databases were searched. Ten journals and reference lists of eligible studies were handsearched. Two reviewers independently screened the studies for eligibility, evaluated the quality, and extracted the data from eligible studies, with confirmation by cross checking. Any disputes were decided by a third person. Meta-analysis was conducted using statistical software RevMan 4.2. After heterogeneity test was done （α=0.05 ） , data without heterogeneity were pooled using a fixed effect model, and those with heterogeneity could be solved by sensitivity＂ analysis, subgroup analysis or random effect model. Results We found eight original trials （n = 3 348 ） that compared medical abortion with surgical abortion, nine trials （n =6 116） that investigating the effect of gestational ages on medical abortion, five trials （n = 1 934） on the use of mifepristone and two trials （n =2381 ） on intervals of administration of mifepristone and misoprostol were located. Quality of foreign studies was better than that of Chinese studies. Therate of complete abortion was higher in surgical abortion group than that in medical abortion group with odds ratio （OR） 0. 18 and 95% confidence interval （CI） 0. 11 to 0.27. The rate of incomplete abortion and abortion failure was higher in medical abortion group with OR 3.32, and 95% CI 1.79 to 6.17, OR 7.36, 95% CI 4. 17 to 12.98, respectively. The rate of complete abortion in the group with gestational age over 49 days was lower than that with gestational age under 49 days with OR 0.51 and 95% CI 0.43 to 0.61. The rate of incomplete abortion and abortion failure was higher in the group with gestational age over 49 days with OR 1.66, 95% CI 1.32 to 2.09 and OR 3.37, 95% CI 2.30 to 4. 94.There were no significant differences observed in the rates of complete abortion, incomplete abortion, abortion failed, time of expelling pregnant sac and time of menses recovery between the single and multi-dosage of mifepristone. Except for the rate of complete abortion, which was higher in 〈48h group, there was a comparable effectiveness for different intervals of mifepristone and ntisoprostol. Conclusions This review showes that it is important to improve the quality of Chinese original studies. Although the effectiveness is better in the surgical abortion group, the rate of complete abortion of medical abortion achieved is 91.6% （1 648/1 800）. This is acceptable for clinicians and women who do not want to be pregnance. The rate of complete abortion is lower in the gestation over 49 days, which had a statistically difference, but little clinical significance. It is necessary to consider increasing the gestational age of medical abortion, especially for those women who have contradictions of surgical abortion or are afraid of operation. Effectiveness of single dosage of mifeprostone is similar to that ofmulti-dosage, but single dosage might be more convenient. This review suggests that shortening the interval ofmifepristone and misoprostol administration should be considered and the best and shortest interval time need to be identified with better evidence.