Electrified railway is a kind of large industrial user with high electricity price. It generates a large amount of braking energy which cannot be measured in reverse. There is no marginal cost to recycle this part of energy through energy storage system, which can improve the economic performance of energy storage system. This paper studied the supercapacitor energy storage system of electrified railway, established charging and discharging strategy and life-cycle economic model. With total investment financial internal rate of return, capital financial internal rate of return and sensitivity coefficient as evaluation indexes, the economic performance of energy storage system was analyzed using actual traction load and typical parameters. The results show that the energy utilization ratio of the energy storage system is low, and it is not advisable to increase the scale of energy storage system too much in order to improve the energy utilization ratio. The high cost of unit capacity is the primary factor restricting the economic performance of energy storage system, the low electricity price takes the second place. In order to improve the economic performance of energy storage system, loan should be used as much as possible for investment and the loan time should be as long as possible.