As a kind of independent commercial assistant, an agent is the common but important commercial subject in market economy. However, the legal concept of the agent is not frequently clear. Practically,the concept of the agent has distinct difference from a commission agent and an agent middleman in the aspects of concept, characteristics, type and so on. Compared with other systems, agent system has many advantages and plays special role. The legal explanation and position of the agent is helpful to effective judgment and adaptability theoretically and practically. The legislation value based on Commercial Regulation of Shenzhen Economic Zone is a main reference to make legal explanation of the agent.