Abstract: Grid computing issues new challenges as resource sharing, coordinate working and autonomous management to cluster operating system （cluster OS）. The current cluster OS with flat structure can not meet the requirements. In this paper, we propose a service-based cluster OS, called DCOS, which adopts hierarchy architecture and object-oriented design, and somehow supports grid computing. Major key techniques as remote procedure invocation, system status detection, real-time check point and security facility are also disscussed.