AbstractRecently Cyber Physical Systems (CPS) have become new research hotspots. Node operating systems (OS) are fundamental systems supporting CPS. When designing CPS especially designing node OS there are still many problems unsolved in aspects of predictability, reliability, robustness, etc. This paper analyzes the needs of node OS and presents two important design characteristics. Based on these analysis we propose a new architecture of node OS. The OS includes Hardware Abstraction Layer (HAL), scheduling module, communication module, development module and other modules, which meets the needs of interactivity and reliability for CPS.