Abstract
Repairable system is complex, because of its diversity distribution form of units’ lives and its complex structure. In this paper we studied on a complex system. Lives and repairing time of units obey general distributions, we got the unit transient availability by using Markov renewal process, then got the system transient availability by using the character of coherent system. Finally gave example which verified by Monte Carlo method. This paper provided calculation base for more complex system.