Abstract: The stress of concrete in the biaxial compression elastic modulus and creep tests is controlled at 30%~40% of the prism specimen's strength at the corresponding age. Compared with the concrete compressive strength testing, the slight unevenness and inclination on the concrete specimen surface as well as the friction between the steel load-bearing board and the concrete specimen have a greater influence on the concrete biaxial elastic modulus and creep tests. In order to reduce the above adverse effects and make the stress and strain of the concrete specimens uniform during the elastic deformation stage, proposing a suitable cushion for the concrete biaxial elastic modulus and creep tests is necessary. By comparing the effects of different materials and composite cushions on the strain deviation rates, strain curves and elastic characteristics when the prismatic concrete specimens are uniaxially compressed, three kinds of composite cushions are choosen and verified in the biaxial elastic modulus tests. The testing analysis results show that the composite cushion with PTFE and geotextile can effectively reduce the vertical and lateral strain deviation rates of the concrete specimen in the biaxial compression elastic modulus tests, uniforming the stress distribution of the concrete specimen. The overall effect of the composite cushion with two layers of 1.0 mm PTFE and 1.2 mm geotextile is optimal.