In this paper, a high reliability, a hard real-time distributed system and its two switch schemes are introduced at first. Then, the realization of switch technology is discussed. Finally, based on the reliability model of hard real-time dual working system, the two switch schemes are analyzed and compared. The conclusions show: The switch in cluster is superior to the switch in node, and it can not only improve the system reliability and real-time, but also reduce the complexity of the program.