Causes of severe oligozoospermia mainly include varicocele or hypogonadism, etc. Chromosomal diseases, etc. can also lead to severe oligozoospermia symptoms in men. 1. Varicocele: Varicocele refers to the symptoms of localized dilatation or obstruction and nodularity of the spermatic veins in men. After the occurrence of varicocele, it will directly affect the quality of semen and semen secretion, which will lead to mild or severe oligozoospermia symptoms, and can be treated with surgery as soon as possible. 2. Low sexual function: If the man himself has low function of the reproductive system or weak sexual function, it will also lead to a decrease in semen secretion and cause severe oligospermia. Most of the low sexual function is caused by congenital pathology, so it needs to be effectively improved through regular physical exercise and physical therapy of reproductive organs. 3. Sex chromosome deletion: When a man has a partial deletion of the Y chromosome during his early growth and development, it can lead to abnormalities in semen production and semen quality, which can lead to severe oligozoospermia. In addition, there are many other reasons that can lead to severe oligospermia, and men should immediately go to the hospital for semen examination and clarify the cause of the disease, and can choose the appropriate treatment under the guidance of the doctor for treatment.