Abstract: In order to design the high safety of safety critical systems, in the paper, the nature of safety of safety critical systems was narrated in detail, established good theory foundation for designing high dependability safety critical systems. At the same time, realization mechanisms of safety were deeply discussed, and high safety safeguard technology based on safety kernel was emphatically researched. In order to realize safety kernel, a kind of programming language based on reflective theory——Open C++ was brought forward, exploring a new approach used to realize safety kernel, at the same time, a novel safeguard mechanism based on safety kernel is adaptable for other safety critical systems.