This paper presents a method for calculating the effective elastic modulus of granular composites based on the model of elastic deformation of porous materials. A distinctive feature of the method consists in averaging the microscopic stress and strain is not like the full volume, but as the effective volume of the phases. Calculated dependence of the averaging effective volume of elastic modulus and the volume content of phases was obtained. The comparison between calculation results and experimental data at different combinations of elastic modulus and arbitrary volume phase concentration was carried out.