The exact dosage of worming drugs for four and a half year old children is determined by the type of drug, the dosage form, and the type of worms, but also pay attention to the contraindications, it is recommended to follow the doctor’s advice to take. At present, the commonly used worming drugs are levamisole, bis(hydroxynaphthyl)thiopyrimidine and so on. 1. Levamisole: It has good efficacy in roundworm, hookworm, pinworm and fecal roundworm disease. Levamisole tablets are used to expel roundworms when the pediatric dose is 2~3mg/kg, hookworms when 1.5~2.5mg/kg. contraindications are hepatic and renal insufficiency, hepatitis active stage. 2. Thiopyrimidine dihydroxynaphthalate: it can be used for the treatment of ascariasis, pinworm disease, hookworm disease, whipworm disease, ascariasis, thiopyrimidine dihydroxynaphthalate tablets are used for driving roundworm and hookworm for 10mg/kg per day, contraindications are allergic to this drug. When children need deworming treatment, they need to go to the hospital for consultation to identify the species of parasites, and then the doctor will choose the suitable drugs for them according to the indications and contraindications of the drugs, and the children need to take the appropriate dosage of the drugs according to the doctor’s instruction. All of the above drugs should be used under the guidance of a doctor.