Abstract: In view of problems of off-line reliability evaluation, the paper proposed a combined model suitable for on-line algorithm for operational reliability evaluation process through research of model of power flow calculation and re-scheduling generation. The combined model not only meets need of engineering applications in aspect of calculation accuracy, but also more importantly shows better performance in aspect of time consumed for calculation through tests with RTS-24 standard system and a real provincial power grid system, which has great practical value in engineering applications.