Hypomagnesemia is diagnosed as clinical hypomagnesemia when the magnesium ion in serum is less than 0.75mmol/L. Treatment principle has two aspects: First, need to actively treat the original disease, exclude or prevent the cause of hypomagnesemia triggers. Secondly, we need to actively replenish magnesium ion through intravenous or through gastrointestinal tract, and at the same time to correct the electrolyte and metabolic disorders. Supplemental magnesium ion has the following aspects: First, when supplemental magnesium, first of all, we must be cautious to supplement magnesium, in addition in serious arrhythmia must be timely supplemental magnesium, intravenous supplemental magnesium ion, encounter patients such as severe renal impairment, need to be in the heart, blood pressure and blood oxygen saturation and other vital signs of monitoring, before being able to supplemental magnesium. Magnesium supplementation process to monitor the concentration of serum magnesium, to prevent the excess of magnesium supplementation into hypermagnesemia, pediatric in intravenous magnesium supplementation, but also pay attention to prevent hypotensive reaction, because magnesium can make the peripheral small arteries vasodilatation. Second, for the lighter hypomagnesemia, can be given through intramuscular injection, such as intramuscular injection of magnesium sulfate and other ways to supplement magnesium ions. If a large number of magnesium ion deficiency, can give intravenous static magnesium sulfate for supplementation. Third, the magnesium at the same time to pay attention to the water electrolyte and metabolic disorders, especially to pay attention to hydration and potassium, because hypomagnesemia, often accompanied by hypokalemia and human dehydration and dehydration.