The invention provides a torsional beam axle assembly with variable stiffness. The torsional beam axle assembly comprises vertical beams (1, 2) and a cross beam (3) connected with the vertical beams (1, 2); the vertical beams (1, 2) are connected with the cross beam (3) through connecting parts (6); the torsional beam axle assembly is characterized in that shearing cavity parts (11) are arranged in the connecting parts (6), shearing members (9) are arranged along end portions (7) of the cross beam (3) in the circumferential direction, and the shearing cavity parts (11) are filled with a shearing thickening fluid composite material (10). According to the torsional beam axle assembly, through use of the shearing thickening fluid composite material, the stiffness of the areas where the crossbeam is connected with the vertical beams can change with changes of vehicle load and deformation, and the reliability of the torsional beam axle assembly is ensured in various load conditions.