Abstract: Based on wave propagating theory of multilayered medium and the optimizing algorithm,the complex elastic modulus of viscouselastic materials are optimized with different physical conditions in order to improve material absorption performance.The absorption performance of bubbled viscoelastic materials is computed and the curves of the optimized elastic modulus are plotted as well.Isoclines of absorption coefficient on complex elastic modulus of absorption materials are presented with certain boundary conditions.Assuming the absorption coefficient is larger than 0.8,the scope of elastic modulus and loss factor of the viscoelastic materials with different boundary conditions are given and discussed.The results show that the sound absorption performance can be improved effectively by adjusting complex elastic modulus of viscoelastic materials.The scope of complex elastic modulus is found to be very sensitive to the boundary conditions while the absorption coefficient is larger than 0.8.The difficulty of adjusting complex elastic modulus can be reduced with certain steel backing.These conclusions are applicable to the case of bubbled viscoelastic materials.