Aiming at different priority of equipment preventive maintenance and corrective maintenance in engineering application, this research applyes phase-type distribution to modeling, and investigates a multi-state warm standby system and a single repair facility of the two kinds of service: Preventive maintenance and corrective maintenance with higher priority, and provides an analytic reliability model that is more appropriate to characterize the real situation. Some important reliability features, such as system steady-state availability, system failure rate and mean time between failure(MTBF), are obtained for certain. Finally, a numerical application is given to illustrate the applicability of Phase-type distribution, and the trend of the system reliability function over time and the influence of the preventive maintenance time and corrective maintenance time on system reliability are discussed, which can demenstrate the strong applied value of the proposed model.