The invention provides a fatigue test device and method for a torsion bar spring assembly. The fatigue test device comprises a first test tooling and a second test tooling. The first test tooling includes a first interface portion connected to the front connecting bracket of the torsion bar spring and a second interface portion connected to the torsion test stand; the second test tooling is provided with an L-shaped plate structure including a first end face structure, a spherical structure and a vertical plate. The first end surface structure is connected to the torsion test stand and disposed on a first side of the L-shaped plate structure including a first stopper structure which is engaged with the torsion bar spring adjusting arm; a spherical structure is matched with an upper cushion of the torsion bar spring and arranged on a second side of the L-shaped plate structure. The vertical plate is parallel to the first end face structure and is provided with a second limit structure concentric with the first limit structure. The fatigue test device has the advantages of simple structure and convenient operation, and uses the universal torsion test bed to simulate the vehicle working condition and completes the bench fatigue test of the torsion bar spring assembly.