Objective: To investigate the clinical features, diagnosis and treatment of oblique vaginal septum syndrome (OVSS). Methods: The clinical data of 80 patients with OVSS admitted to The Second Hospital of Hebei Medical University from July 2005 to July 2023 were retrospectively analyzed. According to the classification system of OVSS proposed by Female Genital Anomalies Study Group, Chinese Obstetricians and Gynecologists Association in 2021, the patients were divided into four groups. The clinical manifestations, accompanied urinary system abnormalities, diagnosis and treatment methods and treatment outcomes were observed. Results: According to the above classification system, among the 80 patients with OVSS, 35 patients (44%, 35/80) were categorized as type Ⅰ, 33 patients (41%, 33/80) were categorized as type Ⅱ, 2 patients (3%, 2/80) were categorized as type Ⅲ and 10 patients (13%, 10/80) were categorized as type Ⅳ. The main onset symptom of patients was periodic abdominal pain (70%, 56/80), vaginal bleeding (20%, 16/80), dysuria or fecal impaction (15%, 12/80), vaginal mucopurulent discharge (10%, 8/80). The morbidity of combined urinary system abnormalities was 88% (70/80), and the most common urinary system abnormality was ipsilateral renal agenesis (81%, 65/80). Bilateral kidneys were normal in 13% (10/80) patients, and 6% (5/80) were combined with other urinary system abnormalities. A total of 74 patients underwent vaginal oblique septectomy or septum excision. Five of the 10 patients with type Ⅳ underwent hysterectomy on the cervical atresia side, 4 patients received hysteroscopy combined with cervicoplasty+oblique septotomy or septum excision, and one patient selected delayed menstruation. Two patients underwent laparoscopic resection of the dysplasia kidney and ectopic ureter which opening to the vagina. Eleven patients with endometriosis cyst, hydrosalpinx or empyema underwent laparoscopic surgery. Conclusions: The main symptom of type Ⅰ and Ⅳ patients is abdominal pain, while the main symptom of type Ⅱ and Ⅲ patients is bleeding. Magnetic resonance imaging (MRI) has advantages in the evaluation of complex OVSS, and MRI is recommended before operation to exclude other axial reproductive tract dysplasia and complex urinary system dysplasia. If there is leakage of urine, vaginal discharge or complex deformity, it is necessary to multidisciplinary discussion and formulate a reasonable surgical plan. The first treatment is related to the prognosis of patients especially children, and should be highly valued.