Intrauterine contraceptive device (IUCD) is relatively safe but still with some serious risks.Uterus perforation is rare and would be fatal.A case of Cu-7 IUCD invading into the sigmoid colon through uterine perforation caused by a pelvic blunt trauma was presented.Our case showed that uterus perforation by an IUCD could induce utero-sigmoid fistula which is likely to be missed.Imaging is required when the patients with IUCD present abdominal pain,particularly with a history of trauma.