Cholinesterase is a protein hydrolase that hydrolyzes acetylcholine. Acetylcholine is a nerve mediator released by cholinergic nerves, such as parasympathetic, motor, and preganglionic fiber endings of sympathetic nerves. When the nerve endings are stimulated and excited, acetylcholine is released, which binds to cholinergic receptors and acts as a neuromuscular excitatory transmitter, and is subsequently hydrolyzed by cholinesterase and loses its effect. If the organophosphorus poisoning, will cause the cholinesterase effect is inhibited, the choline over-accumulation occurs, causing excessive nerve excitation, resulting in organophosphorus poisoning. Clinical measurement of serum cholinesterase activity is useful in the diagnosis of organophosphorus poisoning and in assessing the extent of parenchymal cell damage in the liver.