Left kidney cyst is a structural abnormal disease of the left kidney, which includes simple kidney cyst and polycystic kidney in the clinic. Simple kidney cyst almost does not affect kidney function and has little chance of malignant transformation, so it does not need treatment for patients with no symptoms and no complications. Polycystic kidney is a congenital disease and needs active treatment, it is recommended to choose treatment plan according to patient’s condition: I. Simple renal cyst: 1. Etiology: it can be caused by congenital glomerular and tubular structural variation, or by acquired injury and infection; 2. Treatment: for larger cysts larger than 5cm in diameter, puncture and fluid extraction can be considered and sclerosing agent such as anhydrous ethanol can be injected to prevent recurrence. If the cyst is larger than 5-7cm, accompanied by symptoms of lumbar distension and pain, laparoscopic renal cystotomy can be considered for treatment. Second, polycystic kidney: 1, the etiology: the pathogenesis is unknown, most think it may be related to renal tubular obstruction, local expansion of different parts of the kidney unit; 2, treatment: for patients with normal renal function treatment is based on blood pressure control, including low protein diet, more rest to avoid exertion, while preventing urinary tract infection and renal function damage, such as patients with stone obstruction feasible lithotripsy to remove obstruction. In addition, patients with advanced uremia need long-term dialysis, and those who have the condition can undergo kidney transplantation; patients with severe hypertension or bleeding can have the affected kidney removed.