In this paper, the emergency power supply system for next generation sodium fast reactor (SFR) is investigated to target the latest system design with such as optimized equipment for measure of loss of heat removal system (LOHRS) events, taking into account for strengthening diversity and multiplicity. In addition to diversity and multiplicity, optimization in terms of amount of equipment is also taken into account. The emergency power supply system is consist of emergency generators for design based accident (DBA) and emergency generators to cope with the design extension condition (DEC) in order to power the additional cooling equipment of fuel handling system and reactor core cooling system as a measure for LOHRS event. Base on the load capacity and system operation, the configuration of emergency power supply system was examined aiming optimization of amount of equipment in accordance with some shared use taking into account the reliability. As a result, the emergency power supply system with 4 fixed-type gas turbine generators, 4 portable-type diesel generators and batteries was established.