Abstract: Safety kernel is a new mechanism providing safety assurance in safety-critical system. In this paper, many important concepts and characteristics of safety kernel are discussed by analyzing kernel method, such as the reason for its building, the requirements for its actualization, safety policies and architectures, etc. In addition, a reusable safety kernel mechanism is designed in this paper, which can address common problems found in safety kernel supporting reuse, such as dependencies on specific application software, in harmony of safety parameter expressiveness, etc.