Potassium ion is a very important cellular ion in the human body, its normal range is 3.5-5.5 mmol/L. The role of potassium ion in the human body are: i. The role of maintaining neuromuscular excitability, only if potassium ion is within the normal range, the body’s neuromuscular junction can function normally, in order to maintain normal neuromuscular activity. If the potassium ion concentration is too high or too low, it is easy to appear weakness of the limbs and other situations. Second, potassium ions play an important role in the normal activities of the heart muscle, potassium ions within the normal range, the electrophysiological activities of the heart muscle to maintain normal function, if the potassium ion concentration is too low, the conduction system of the heart muscle will slow down, if the potassium ion concentration is too high, there will also be rapid heartbeat, cardiac arrest. Third, potassium ions play an important role in maintaining the normal function of the nervous system. Patients with low blood potassium will show symptoms of mental depression, indifference and disinterest in everything.