Abstract: Based on the analysis of the safety related ARINC653 specification, an scheme of embedded real time operating system being suitable for safety critical applications:S-CRTOS, is proposed in this paper. The principle of isolation and protection is introduced in details, and several critical technologies:partition schedule, process pool and asynonous mechanism, are also described. This design has been implemented at some target boards, and can be used for safety critical systems:avionics electronics and automobile electronics etc.