Multi-Agent Systems (MAS) are an emerging paradigm that has high potentials for developing distributed, open and concurrent complex systems. These systems often need to operate in dynamic environments and face the challenges of handling continuously changing requirements. These aspects increase the complexity of designing MAS. To handle the complexity and facilitate reasoning, software architecture is now recognized as the best way to meet these expectations. In this paper, the authors try to handle these issues by proposing a new approach for modeling and analyzing MAS architectures by using a formal specification of the Bigraphical Reactive System (BRS). The feasibility and the advantage of the proposed approach are shown thru a case study.