The muscarinic-like symptoms of organophosphorus poisoning are also known as M-like symptoms. It is mainly a hyperexcitation of the parasympathetic nerve endings, which produces muscarinic-like effects. One manifestation is smooth muscle spasm leading to pupil constriction. Inspection of the pupil with a flashlight reveals that the patient’s pupil is very small and even shows a pinpoint pupil. At this time, if atropine is used, the pupil of the patient is observed after the drug is administered, and the pupil of the patient changes from small to large in the case of effective drugs, reaching 4-5 mm or even the edge of the eye.