order to study the effect of compressive stress and shape factors on the vertical stiffness of square laminated rubber bearings, serial compression tests were conducted on four 400×400 mm2 full scale square laminated rubber bearings at stresses of 10 MPa，12.5 MPa and 15 MPa. The relation between the vertical stiffness, shape factors and compressive stress of the four bearings was studied and an experimental expression was obtained. The tests and analysis results have shown that the vertical stiffness of the laminated rubber bearing is compressive stress dependent, the vertical stiffness increases when the compressive stress increases; at constant compressive stress, the increase of the second shape factors will lead to the increase of vertical stiffness; and the compressive stress has more influence on vertical stiffness when the bearing has a large second shape factor value.