Recently, with the increasing complexity of applications based on network, many complex systems have appeared to be typically autonomous, open, dynamic, and heterotopous. These systems make current software theories and technologies confront with many challenges, one of which is that mechanisms need to be provided with these complex systems from the point view of software architecture. Agent technology provides higher level abstractions and more natural style, which is different from object orientation and well suited to tackle the complexity, to specify and design software systems. However, component and the relationship between component and agent in software architecture of multi-agent system (MAS) are understood from the perspective of object-orientation. Many existing agent-oriented methodologies see agent class or agent type as the component, but agent is still the instance of an agent class or agent type, which doesn't meet the requirement of the dynamic property of complex systems. In this paper, the motivation of component in software architecture of MAS is analyzed, a dynamic binding mechanism for the relationship between component and agent is proposed, four basic operations based on Caste: join, quit, activate and inactivate are put forward, and the operational semantics is defined, in order to implement the high-level model for MAS architectures.