During casual inspection of Dehong Prefecture Animal Health Supervision Institution of Yunnan Province，it was found that one veterinary drug service department was suspected of selling inferior drugs. Based on investigation by local agricultural bureau，the criminal facts were ascertained clear and the evidence was insufficient. According to the Veterinary Drug Management Regulations，administration penalty was imposed. Here，some law enforcement contents including the case source，investigation process and the handlng situation were emphatically introduced，and some problems were analyzed，such as the nature of the case，the suitability of law enforcement subjects，application of discretion，as well as the protection of the legitimate rights and interiests，hoping to provide reference for the investigation and handling of similar cases.