The invention provides a system and a method for improving power supply reliability based on big data. Multiple reasons such as a power failure user, a power failure duration, a power failure reason, a power failure plan, a collection terminal, weather, power failure equipment, equipment life, equipment quality, months/seasons and the like related to a power supply and power failure event are analyzed based on big data analysis to obtain influence ratios of different influence factors on the power supply reliability, and regular updating is performed along with continuous development of a power grid. The power supply reliability is predicted according to the influence ratios in different time periods, and a power supply and power failure plan and working arrangement of overhaul and the like are guided according to a monthly reliability index target value and a fluctuation interval sent to provincial or municipal companies by a state grid company, so that the purpose of improving the power supply reliability is achieved.