Whether left ovarian teratoma is serious or not is related to the tumor histopathology, benign ovarian teratoma is mostly not serious, malignant ovarian teratoma is more serious. Left ovarian teratoma is a benign tumor, that is, ovarian mature teratoma, most of them do not have obvious symptoms, found by accidental physical examination, the treatment is given to the ovarian teratoma excision or left ovarian salpingo-oophorectomy, the recurrence rate is low after the operation, and women who have the requirement of childbearing can retain their reproductive function, generally the impact is not significant, and most of them are not serious. Left ovarian teratoma is a malignant tumor, i.e., immature teratoma of the ovary. Tumor recurrence rate and tumor metastasis rate is high, and signs such as emaciation, severe anemia, and cachexia appear in the late stage. Most of them need chemotherapy after surgical treatment, which is more serious and threatening to patients’ life and health. Mature cystic teratoma malignant formation of squamous cell carcinoma, poor prognosis, more serious. In the clinical left ovarian teratoma patients need to consult the doctor in time, under the guidance of professional doctors according to the specific circumstances to give personalized treatment.