The invention discloses an automobile chair fatigue testing device. A dummy hip is hinged with a dummy backrest by a hinge shaft, the upper ends of a first fixed plate and a second fixed plate are connected and supported by a first turn buckle, and the inclination angle of the dummy backrest can be adjusted by adjusting the first turn buckle; a rotary telescopic mechanism is composed of an upright post, a cross rod, a cylinder, a force transducer, a fixed end and a Morse cone; the bottom of the lower section of the upright post is hinged to the second fixed plate, a second turn buckle is connected between the upper end of the lower section of the upright post and the second fixed plate, and the lower section of the upright post is connected with the upper section together by the Morse cone; the cross rod has two sections which are connected by the Morse cone, one end of the cross rod is connected with the upright post, and the other end of the cross rod is vertically connected with the cylinder, the force transducer and the fixed end. The device can reduce the fatigue strength of experimenters, reduce the test time and accomplish fatigue test of a chair height adjusting handle and unlocking fatigue test of a chair slide rail.