To find out the rate of repeated induced abortion among unmarried abortion women and to study the relevant risk factors. From July to September 2005, we used the method of hospital based descriptive epidemiological study to investigate 2295 abortion women below 25 years of age in Beijing, Shanghai and Zhengzhou. Case-control study was used as the method. We considered the women with history of repeated abortion as case group (736 women) and considered the women without history of repeated abortion as control group (1559 women). The mean age of respondents was 21.92 years with minimal age as 15 years. 17.2 % aborted women aged below 20 years with 32. 1% of them were ever having a history of previous induced abortion. Among 736 women with repeated abortion, 75.3 % of them had one time of induced abortion previously, 18.1% having two times, 4.2% having 3 times, 13 women having 4 times and 4 women having 5 times and one even with the maximum of having 8 times of previous abortion. In comparison with control group, the case group had higher rate among women whose first sex was below 18 years (16.2% vs. 9.4% , P<0.01). There were higher rates of women under following conditions: having exposed to sexual behavior for more than 3 years (33.6% vs. 6.6 % , P<0.01), having cohabited with male partner for over 1 year (64.6% vs. 23.9%, P <0.01), having regular sexual life (48.5 % vs. 37. 1%, P < 0.05), having multiple sexual partners (36.0% vs. 15.0%,P<0.01) having unwanted sex (6.0% vs. 3.9%, P<0.05), whose current pregnancy resulted from contraceptive failure (39.3% vs. 31.6%, P< 0.01), having a history of high-risk abortion (30.8% vs. 3.1%, P< 0.01) etc. In comparison with the control group, the case group showed higher rates of male partners not supporting this induced abortion, male partner not participating in decision-making on abortion and male partner not accompanying the female partners to seek for abortion service (rates of the three major factors in case group and in control group were 10.3% vs. 5.9%, P< 0.01, 30.3% vs. 24.0%, and 27.5% vs. 23.5%, P<0.01, respectively). The rate of repeated induced abortion among unmarried abortion women was relatively high. The risk factors for females would include: younger age of sex debut, longer duration from the beginning of first sex to the current abortion, cohabitation, regular sexual life, multiple sexual partners, unwanted sex, contraceptive failure and high risk induced abortion. Meanwhile, unmarried but repeated abortion was related to the differences of gender between males and females and male partner's concern on induced abortion.