Abstract： Objective To evaluate the effectiveness of carboprost methylate suppository for cervical ripening before diagnostic hysteroscopy in premenopausal women. Methods From July 2014 to July 2015, 1614 women who were undergone diagnostic hysteroscopy in 12 hospitals were randomly assigned into study group(n=1209)and control group(n=405). The cases in study group were given 1 mg carboprost methylate suppository in vagina before hysteroscopy, the cases in control group were given 1 mg placebo. The extent of cervical ripening, the time of dilated cervix, pain scoring, incidence of drug side reactions after 24, 48, 72 hours, satisfaction degree of operators and patients, the time of hysteroscopy, incidence of complications between the two groups were observed and compared. Results (1) Mean cervical widths in the study and control groups were 6.11 ± 1.11 and 5.95 ± 1.11, and showed a significant difference(P=0.034);the percentage of women requiring cervical dilatation in study group was lower than the percentage in control group significantly [28.3％(342/1209)versus 34.6％(140/405), P=0.020].(2) The time of dilated cervix in study group was shorter than the time in control group significantly [(34 ± 25) versus(52 ± 49)s, P=0.028] for the patients whose mean cervical widths≤4.(3)There was no significant difference in pain scores between the two groups(P>0.05).(4)The incidence of side reactions 24, 48, 72 hours after operation were no significant difference between the two groups (P>0.05). (5) The satisfaction degree of operators and patients, the time of hysteroscopy, incidence of complications between the two groups were no singnifcant difference between the two groups (all P>0.05). Conclusion Application of carboprost methylate suppository by vagina before hysteroscopy is an effective and safe method of cervical ripening.