Mannitol injection has the effect of dehydrating tissues as well as diuretic. It is usually used for various causes of cerebral edema, elevated intraocular pressure, nephrotic syndrome, cirrhotic ascites, as well as being effective in some drug toxicities. Mannitol is mainly used for tissue dehydration or osmotic diuresis due to its high osmotic pressure. Its tissue dehydration effect can treat cerebral edema of various causes, reduce intracranial pressure and prevent the formation of cerebral hernia. Mannitol can also be applied in patients with elevated intraocular pressure when other medications are ineffective. When other diuretics are ineffective in patients with nephrotic syndrome and cirrhotic ascites, mannitol can be applied to assist diuresis. For barbiturates, salicylates, bromides and other drugs toxicity can be applied mannitol to promote the excretion of the above substances to prevent nephrotoxicity. The more common adverse reactions of mannitol include electrolyte disorders, oliguria, hemorrhage, osmotic nephropathy, etc. Mannitol is contraindicated in patients with acute tubular injury, hemorrhage, and acute pulmonary edema. The drug is a prescription drug and should be used in strict accordance with medical advice.