Fluid balance disorders are very common pathophysiologic changes in clinical practice, including disorders of water, electrolyte, and acid-base balance. Either type of balance disorder will cause metabolic disorders in the body, and further deterioration can lead to organ failure or even death. Therefore, how to maintain the patient’s water, electrolyte and acid-base balance, and how to correct the resulting balance disorder in a timely manner has become the primary task of clinical work. The main components of body fluids are water and electrolytes. It is divided into two parts, cellular and extracellular fluid, and its amount varies with gender, age and fatness. The amount of body fluid in adult males is generally 60% of body weight; the amount of body fluid in adult females is about 55% of body weight. Children have less fat, so the proportion of body fluid to body weight is higher, in newborns, up to 80% of body weight. The amount of body fat increases with age, and after the age of 14, the proportion of body fluid in children is similar to that in adults. An imbalance in fluid balance can cause disturbances in the body’s equilibrium. Disorders of fluid metabolism and acid-base balance are often associated with or a consequence of a primary disease. Prompt measures should be taken to prevent the occurrence of such disorders. Generally, about 1,500 ml of 5%-10% glucose solution, 500 ml of 5% grapefruit saline, 130-40 ml of 10% KC can be injected intravenously every day to replenish the daily requirement of water and glucose, so as to economize the protein catabolism and to avoid the ketoacidosis that may occur when excessive fat burning occurs. For patients with fever, the amount of supplementation can generally be increased according to the standard of about 3～5ml/kg of hypotonic body fluid lost from the skin for every 1℃ rise in body temperature. For patients with moderate sweating, the loss of body fluids is about 500-1000ml (containing NaC 11.25-2.50g); when sweating a lot, the loss of body fluids is about 1000-1500 ml. For patients with tracheotomy, the daily evaporation of water from respiration is 2-3 times more than the normal one, which is about 1000ml. All of them need to be increased in rehydration.