Pelvic ureteral junction obstruction (PUJO) is the most common cause of pediatric hydronephrosis. Due to the popularity of prenatal ultrasound, most congenital hydronephrosis can be detected in utero, so parents need not worry too much. For mild to moderate hydronephrosis, if there are no symptoms, intravenous pyelogram should be done after full term to understand the degree of hydronephrosis and renal function, such as below moderate hydronephrosis can be monitored by ultrasound, but there is no need to rush to surgery. Surgery can be postponed to 6 months-12 months later. In case of severe hydronephrosis, or symptomatic hydronephrosis, surgery should be performed if the hydronephrosis is gradually aggravated during follow-up. Even for huge hydronephrosis, the authors of this article feel that we should try to do a disconnected pyeloplasty to preserve the kidney according to the ECT results. For bilateral hydronephrosis, I have completed more than 30 cases in one phase with better results, shortening the course of the disease and reducing the pain of the child and the ideological and economic burden of the parents. Special care should be taken not to easily remove the kidney with severe hydronephrosis, which will cause irremediable regret.