Perioperative prophylactic medication, mainly preoperative antibiotic intravenous drip or local medication, is aimed at preventing contamination of the incision as well as the organ during surgery. The principle of preventive medication requires attention to the type of surgery, the degree of trauma and the bacteria that may contaminate, the sensitivity to drugs, and the principle of using as single as possible, for drugs with stronger contaminating bacteria. For surgery via the skin category, drugs that are more sensitive to Staphylococcus aureus can be selected; for surgery via the colorectum, drugs that are sensitive to intestinal Gram-negative bacilli can be selected. The drug is given within 0.5-1 hour before the surgical skin mucosal incision.