Power supply reliability (PSR) is a critical factor in the optimal configuration of standalone microgrids. Considering the impact of the failure outage of power generation and energy storage equipment, as well as the uncertainty of renewable energy on PSR, a multi-objective bi-level mixed-integer optimisation model is proposed. Based on Benders decomposition, the model is decoupled into a master problem (MP) of the equipment optimal configuration considering economy and environmental conservation and a subproblem (SP) of the PSR check. Considering the load importance hierarchy, two types of slack variables are introduced into the SP to ensure both the reliable power supply of important loads and the PSR of the system. Through interactive iteration of the MP and SP, the complexity of the optimisation model is considerably reduced, improving the solution efficiency while ensuring the rationality of the optimal configuration scheme. Finally, the effectiveness of the proposed model is verified by a typical stand-alone windphotovoltaic-diesel-battery microgrid system and analysed in terms of the impact of reliability requirement and energy storage on the configuration scheme and algorithm convergence.