Abstract: Aiming at the uncertainty of distribution network power supply reliability resulted from distributed energy（DERs）access,a two-layer model for optimal configuration of hybrid energy storage system（HESS）in distribution network considering power supply reliability is proposed. Firstly,the typical load timing curves for five types of load users and the typical output timing curves for wind power and photovoltaic units are extracted. Based on the sequential Monte Carlo method,a simulation model is established to assess the power supply reliability of distribution network,taking into account DERs islanding,random HESS faults and various operational strategies. Secondly,to optimize HESS operation during distribution network failures,a two-layer model for multi-objective optimal configuration of HESS in fault power outage scenarios is developed,incorporating charging and discharging strategies based on HESS capacity and power points. Finally,the improved IEEE-31 node system is used for case study validation. The results show that the proposed model can improve the comprehensive power supply reliability of distribution network by 0.118%,and significantly increases the DERS consumption by more than 30%.