The invention relates to an air spring's cycle life testing tool which comprises a work station, two sliding supports symmetrically arranged to each other, a connecting rod and an air cylinder. The facing surfaces of the two sliding supports are provided with a pair of air spring connection bases. The work station is provided with tracks for sliding supports to slide along. One end of the connecting rod is hinged to the sliding supports while the other end is hinged to the pistol of the air cylinder. According to the invention, the air cylinder in the tool controls two sliding supports to move in opposite directions. Compared to the traditional manner where one end of an air spring is fixed while the other is moveable, the telescopic scope of the air cylinder pistol in the tool is reduced, therefore, consuming less energy, saving time and cost.