This paper defines the concept of police with definitions of "specific plus differential" from the angle of Science on Public Security

taking formal logic ways. In the "specific" aspect

this paper defines police as functional subject from historical dimension

academic dimension and legislative dimension. It benefits making a distinction between police

police affairs

police behaviors

police bureau and police power in case of unnecessary controversy. It benefits preventing the participation of informal main police power such as private police forces and auxiliary police officers to promote the professionalization

professionalism and standardization of police. It is also helpful to promote the development of Science on Public Security. In the "differential" aspect

through the limitation of nature

purpose and method

we find out that class nature is the natural characteristics of police. It is an important factor to distinguish police from other subjects. It is also sharp weapon to prevent welfare police theory and police neutrality theory. The purpose of police is multilateral and continuously developing. It should be society control including negative factors and positive factors and assistant factors. Coerciveness is the specific method of police. Coerciveness of police methods doesn't reject non-powerful methods such as guide

service and assistance.