Objective To analyze the etiology of hyponatremia in patients with hydrocephalus after ventriculoperitoneal shunt (V-P shunt) and to investigate the therapeutic method.Methods The patients who had clinical symptoms and imaging manifestations of the hydrocephalus were selected as subjects and received V-P shunt. The electrolytes were measured after V-P shunt and the patients whose serum sodium concentrations were below 120 mmol/L were considered with serve hyponatremia.Results One patient was cured by simple salt supplement, one patient was cured by salt supplement and oral prednisone, and three patients were cured by salt supplement, oral prednisone, and increasing the pressure of catheters. Conclusions All patients with hyponatremia are confirmed as having cerebral salt wasting syndrome. The etiology of hyponatremia may be that the hypothalamus or other sites cannot adapt to the sudden change in intracranial pressure.