Abstract: A SRN model for a two-node hot-standby cluster of process control system in process industry was constructed, in which a precise description about the system status and behavior of permanent failure and intermittent failure was proposed and both raid share and image share were considered. The availability of the system was simulated and analyzed using SPNP package. The results showed that image share could obviously enhance the availability of the system compared with raid share in the same condition. Reducing the time of failure discovery and increasing the speed of failure repair could also improve the availability.