ObjectiveTo probe into the clinical effects of intra-amniotic injection of ethacridine with Cook cervical ripening balloon in terminating mid-pregnancy. MethodsA total of 150 mid-pregnant women who required induction of labor from January 2011 to December 2012 were randomly divided into two groups: observation group (intra-amniotic injection of ethacridine with Cook cervical ripening balloon) and control group (intra-amniotic injection of ethacridine). ResultsThe time of labor induction was obviously shorter in the observation group than the control group [the time from using ethacridine to contraction: （29.68±4.17） vs (33.60±5.38) hours, P<0.05; total process: (7.63±2.30) vs (9.86±3.20) hours, P<0.05], and the residual rate of placental membranes [28.6% (10/35) vs 56.4%(22/39), P<0.05] was significantly lower. But there was no significant difference in postpartum hemorrhage [(81.60±17.64) vs (83.82±15.08 ) mL, P>0.05] and rate of success [100.0% (35/35) vs 94.9% (37/39), P>0.05]. ConclusionTerminating mid-pregnancy by intra-amniotic injection of ethacridine with Cook cervical ripening balloon has the advantages of shorter time and less pain, which deserves clinical application widely.