The major challenges traditional operating system (OS) design faces are the increasing number, diversity, and distribution scope of resources to be managed and the frequent changes in system state. However, the structures of existing OSs have become the biggest obstacle to solving the above problems as (1) tight coupling and centralization of the structure lead to poor flexibility and scalability and separate OS ecology; (2) contradiction between various capabilities, e.g., security and performance, due to the unitary isolation mechanism such as kernel-user isolation. Therefore, this study combines the hierarchical software bus (softbus) principles with isolation mechanisms to organize the OS and proposes a new OS model termed Yggdrasil. Yggdrasil decomposes an OS into component nodes connected by softbuses, whose communications are standardized to message passing via the softbus. To support the division of isolated states such as supervisor mode and different software hierarchies, Yggdrasil introduces bridge nodes for cascading and controlled communication between softbuses, and enhances the logical representation capability and scalability of OS through self-similar topology. Additionally, the simplicity and hierarchy of the softbus help to achieve decentralization. To verify the feasibility of Yggdrasil, the study builds hierarchical softbus model for OS (HiBuOS) and demonstrates the feasibility of developing a new OS based on Yggdrasil’s ideas through three specific designs: (1) designing and planning a hierarchical softbus structure according to the scale and requirements of the target operating system; (2) selecting specific isolation and communication mechanisms to instantiate bridge nodes and softbuses; (3) realizing OS services based on the hierarchical softbus style. Finally, the evaluation shows that HiBuOS has notable potential and advantages to enhance system scalability, security, performance, and ecological development without significant performance loss.