Xiao Li, a lively and lovely senior high school student, suddenly felt severe pain in her right lower abdomen one day during physical education class and was sent to the hospital. It was suggested that the right ovarian teratoma might be reversed, and a caesarean section was performed immediately. The right ovarian teratoma was found to be 8 cm in size, with 720 degrees of torsion, and the whole ovary including the fallopian tube was blackish-purple. Due to the obstruction of blood supply to the ovarian fallopian tube after torsion, the tissue was ischemic and necrotic, and the right ovarian fallopian tube could only be resected. Ovarian teratoma is a benign tumor derived from germ cells, accounting for about 10-20% of all ovarian tumors, and is more likely to occur in young women. Germ cells can differentiate into various tissues in the body, so the tumor may contain skin, hair, grease, teeth, cartilage and other components, and the specific gravity of these tissues is different, so that the center of gravity of the tumor is often tilted to one side. Once the twisting occurs, it will cause ischemic necrosis of ovarian tissues or induce tumor rupture, which will cause serious chemical peritonitis. In addition, about 4% of ovarian teratomas will become malignant. Due to the large space in the abdominal cavity, early ovarian teratomas often have no conscious symptoms and are often detected only when acute abdominal pain occurs after tumor torsion or rupture, but the best time to preserve the ovaries is lost at this time. Pelvic ultrasonography is a common tool to diagnose ovarian teratoma. Teratomas are composed of different tissues, so ultrasound will show a special sonogram to help the doctor differentiate them from other ovarian masses. Ultrasound has a 98% accuracy rate in diagnosing ovarian teratoma, even when the tumor is only 1 cm in size. To avoid complications such as tumor torsion, rupture, infection and malignancy, ovarian teratoma must be removed immediately once it is diagnosed. Pneumoperitoneum-free laparoscopic ovarian teratoma excision is used for ovarian teratomas of all sizes. The tumor can be completely removed while preserving normal ovarian tissue and function. The procedure is safe, convenient, with minimal damage and quick recovery.