Based on the laws of the minimal thermal resistance and the specific effective thermal conductivity, this paper predicts the effective thermal conductivity of composites filled with different shape particles. When the particle shape is equivalent to the cube which used character length of particle in the direction of heat transfer as edge length, the dimensionless relative character length is amended using the volume ratio of the cube and factual particle as shape factor. Based on the shape factor, 〖BP(〗it developed the〖BP)〗 universal expression of the effective thermal conductivity is developed, which is adaptive to the composites filled with different shape particles and its volume fraction is medium and lower. The calculation results of the universal expression accord well with that of experiments and other models, the effective thermal conductivity increases in direct proportion to shape factors for heat conduction enhanced composites when volume fraction is invariable, and the thermal conductivity of composites can be enhanced by increasing the dimension of particle in heat transfer direction.