With the high penetration of renewable energy sources, the reliability of power systems becomes morevulnerable than ever because of the greater uncertainty and intermittence in power generation. Reactive power plays animportant role in the power system reliability, because it isclosely related to the system voltage stability and voltagecollapse. However, reactive power-related reliability issuesare seldom emphasized in conventional power reliability evaluations. This article investigates power system reliabilityof real and reactive power. Real and reactive power shortages and the associated voltage violations due tosystem failures are considered on reliability evaluation ofpower systems. A three-stage load-shedding technique forpost contingencies is implemented to determine the contributionsof real and reactive power on the system reliabilityand to find an optimal way to release networkviolation. The results provide the detailed information on power system planning and operation for system plannersand operators from real and reactive power aspects.