The invention discloses a usage method for electromagnetic recognition machine. A supporting rod is fixed on the cashier position of the front gate of the bus, and a fixed base is arranged on the supporting rod, which a rotating cylinder connected to the fixed base thread is capable of rotating on the circular bulges. The height of the fixed base is adjusted, the rotating cylinder is rotated to force a fixed block rotating too, and a clamping block connected to the fixed block in a hinge mode is cooperated with the bulges, so the fixed base fixedly installed on the supporting rod is carried out. A spring is arranged between the clamping block in L-shaped and the rotating cylinder inner wall also, a certain vibration is occurred on the connection place between the clamping block and the bulges when the bus body is shock violently on the road, especially on the bumpy road, the stress made by the vibration is removed through the spring compression deformation.