The invention discloses a device for measuring air leakage of a power station boiler air pre-heater. The device comprises at least one gas sampling gun, two gas mixers, a gas sampling switchover tee joint communicated with the gas mixers, a sucking pump communicated with the switchover tee joint and an oxymeter connected with the sucking pump, the gas sampling guns are arranged at an inlet flue and an outlet flue of the boiler air pre-heater respectively, and the two gas mixers are communicated with the gas sampling gun at the inlet flue and the gas sampling gun at the outlet flue respectively. The gas sampling guns are arranged, multi-point simultaneous sampling on the flues is achieved, the measurement result is more accurate, and the device can meet testing regulation requirements. Control sampling on different gas inlet pipes can be achieved through the gas mixers, the air leakage problem of the mixers can be effectively and completely eradicated through sealing liquid, and measurement reliability is improved. The oxymeter is adopt to measure inlet and outlet gas components, measurement errors caused by instrument precision are eliminated, and measurement precision is improved.