Abstract:From the origin of laws, subject identity, basis of function and power, duty’s attribute, procedure principle and responsibility, the law enforcement by police in plain clothes can neither be expanded in use, nor can be abused without any principle. Moreover, it cannot be used as a normal enforcement means. Such enforcement is difficult to agree with the ideolog- ical line of rule of administrative law, meet the demand of“technical parameter” of administration according to law, and active- ly adapt it to the innovative thinking of modern rule of law.