1. Authors have experienced 1 case of ovarian cyst complicated with torsion of Pedicle and rupture in puerperium. 2. This is a case of pseudomucinous cyst with partial carcinomatous change, such a complication of pregnancy with malignant ovarian tumor is rather rare. 3. The relation between pregnancy and ovarian tumors particularly malignant ovarian tumors, and the role of oregnancy and delivery in torsion of pericle and rupture of tumor were discussed.