Cryptorchidism is a condition in which one or both testicles do not descend into the scrotum and remain anywhere along the way. When the male fetus develops in the mother’s body, the descending process of its testicles is obstructed and “anchored” in the descending way, and the testicles cannot be found in the scrotum, so cryptorchidism occurs. There are mainly the following factors: (1) Anatomical factors include: (1) In embryonic stage, the testicular ligament is very short or defective, which does not allow the testis to descend adequately; (2) Adhesion between testicular ligament and peritoneum occurs, which makes the testis unable to go down; (3) Abnormal development of blood vessels of testis is curved or folded, which restricts testis descent by pulling it from the upper part; (4) Blood vessels of the spermatic cord or the vas deferens are too short; (5) The volume of testis is too large. If the inguinal canal is too tight or the opening into the scrotum at the distal end of the external ring is lacking, the testis cannot enter the scrotum; ⑥ Abnormal development of the scrotum, the scrotum is too small to accommodate the testis. (2) Endocrine factors The descent of testis should have enough power, that is to rely on maternal gonadotropins to stimulate fetal testicular mesenchymal cells to produce androgens, therefore: (1) when the testis itself is defective, it does not produce descent response to gonadotropins and cryptorchidism occurs; (2) because the descent of testis occurs when the concentration of gonadotropins in the blood is very high, therefore, when the mother has a lack of gonadotropins, this also leads to incomplete descent of the testis. (3) Genetic factors Some patients with cryptorchidism have a significant family history, so genetic factors may be one of the causes of cryptorchidism. There may be other reasons for cryptorchidism, and it is expected that with the continuous improvement of medical level, these reasons will be clarified one by one, so as to find out the effective prevention and treatment methods to stop the occurrence of this disease.