Based on the model of Ningxia public commercial information service platform for SOA, this paper proposes architecture of multi-agent system (MAS) of public commercial information service platform. In the MAS of this architecture, the human-computer agent, the service agent, the service bus agent and the interface agent correspond to the interactive service layer, the application service layer, the commerce information service bus layer, and the business service interface layer and the business layer. And then it offered a norm-based cooperation and coordination mechanism of agents to increase the efficiency of collaboration. The research provides a basic framework for the cooperation, conflict resolution and organizations among agents of the MAS of Ningxia commercial information service platform. At last, an application is given.