Diabetic ketoacidosis is an acute complication of diabetes mellitus, and rehydration is a very important measure in the treatment of diabetic ketoacidosis. The principles of rehydration in ketoacidosis are as follows: First, salt then sugar, in the case of hyperglycemia, saline should be given intravenously first, and when the blood glucose falls below 13.9 mmol/L, it can be changed to sugar-containing liquid, and insulin should be added appropriately to prevent the blood glucose from rising again. Second, first fast and then slow, in the early stage of diabetic ketoacidosis treatment, the body loses fluid seriously, so it can be fast drip, and gradually slow down the drip rate. Third, crystal first and then colloid, when rapid rehydration still exists low blood pressure or signs of shock, colloid infusion or anti-shock treatment is required. IV. The fluid loss in diabetic ketoacidosis is serious and can reach 8%-10% of body weight, which can be replenished within a few days. V. In the process of rehydration, potassium should be recharged at the same time, and attention should be paid to monitoring vital signs, cardiac function, renal function, etc.