Abstract: A Multi-Agent Systems Model (MASM) is presented from the point of view of software architecture, in which Object-Oriented Petri Nets (OPN) are adopted as formal theory bases. The OPN are used to visualize architecture and system behaviors. Based on MASM, a practical toolbox for MAS (MASDT) is designed and developed, which can effectively and efficiently support the development of complicate applications. Finally, MASM is used to model and analyze the intelligent gas station, and the prototype is developed with the help of MASDT. This work has enriched the design and development theory for multi-agent systems.