The invention discloses a system and method for measuring long air gap lightning stroke discharging electron temperature, and relates to the technical field of electric systems. The system and method are used for acquiring high-precision electron temperature in the streamer-guidance conversion process, improving the deep degree of discharging physical mechanism research under long air gap lightning impulses, and finally improving the lightning preventing capacity of the electric systems. The system for measuring the long air gap lightning stroke discharging electron temperature comprises an impulse voltage generator, a capacitive voltage divider, a measuring resistor, a first bar electrode, a second bar electrode located above the first bar electrode, a spectrograph, an ICCD camera and an oscilloscope. The measuring system in the technical scheme is applied to the method for measuring the long air gap lightning stroke discharging electron temperature. The system and method for measuring the long air gap lightning stroke discharging electron temperature are used for study of lightning defense of the electric systems.