Abstract Global reliability (g-reliability) of any complex system is defined and two simplified different methods for evaluating the same are proposed. Both the proposed methods are conceptually simpler and computationally efficient for g-reliability evaluation of any large complex system and effectively applicable to its proper form. They therefore require less computer memory and computational efforts as compared to other existing methods. Proposed methods are applicable to the network having both nodes and branches of finite non-zero failure probability. The efficiency of each method increases with the complexity of the network. Both the proposed methods are also illustrated with examples to demonstrate the effectiveness of each method.