Paraquat is the most toxic pesticide among pyridine herbicides and its absorption rate in human body is about 5%-15%, the lethal dose is about 30-50mg per kg of body weight. after oral administration of paraquat in excess of the poisonous dose, it will be distributed in large quantities in various important organs and tissues of the body within 6-18h, which can cause myocardial damage and toxic myocarditis; lead to multi-organ failure and eventually lung failure. Severe cases will eventually die of pulmonary failure. Paraquat is corrosive and patients may experience burning sensation in the mouth and throat in the early stage. Most of the patients may have large ulcers in the mouth, tongue and throat and esophagus in 2-3 days after taking the drug, accompanied by nausea, vomiting, loss of appetite, abdominal pain and diarrhea, and some patients may have blood in the stool. Pulmonary symptoms will appear within 1-2 weeks. Patients with mild lung damage may only show cough, shortness of breath, chest tightness and chest pain; however, patients with more serious lung damage will have obvious respiratory difficulty, which is obviously aggravated after activities. Patients may have rapid heartbeat and cyanosis of mouth, lips and face. If paraquat reaches 20-40mg per kg body weight in the body, it can progress to pulmonary fibrosis, leading to death of the patient due to respiratory failure, and the course of the disease is usually in 2-3 weeks. If the amount of paraquat absorbed into the body reaches more than 40mg per kg body weight, the damage to the gastrointestinal tract, liver, kidney and lung will be very serious and the disease will develop more rapidly, most patients die within 1-7 days after taking the drug.