Reliability and availability have always been important characteristics of systems but become even more critical and complex issues on networks. Due to the high complexity of accurate calculation methods, simulation methods for network reliability and availability evaluation have been a popular area of research, and received significant attention. In this paper the network topology model, the failure driven simulation method and the reliability and availability statistical algorithms are put forward, and then the network reliability and availability simulation flow based on the Monte Carlo method was designed. This simulation method can be used to calculate the reliability and availability of a network whose nodes and links may be failure. Two repair policies, immediate repair and delay repair, are provided to choose. Finally, the backbone of CERNET (China Education and Research Network) is taken as an example and the simulation results are analyzed.