Water and sodium in the body must be maintained in a certain amount and ratio for blood sodium to remain normal. If the water discharge is reduced or exceeds the body’s ability to drain water because of drinking too much water or too many water transfusions, resulting in a significant excess of water in the body, sodium is diluted, and the sodium ion concentration in the blood drops, it is called dilutional hyponatremia, and dilutional hyponatremia is also called water intoxication. The decrease of sodium ion concentration in blood will lead to the decrease of blood osmotic pressure, and the excessive water will enter into the cells causing cell edema, especially the brain cells edema will cause the pressure in the brain to increase, and the patient will have headache, drowsiness and restlessness alternately, mental confusion, delirium, and even convulsions and coma. Treatment focuses on controlling water intake, diuresis, and dehydration, and untimely treatment can lead to patient death. Dilutional hyponatremia often occurs in patients with poor renal function, poor cardiac function, and cirrhosis of the liver, and these patients especially need to pay attention to controlling water intake.