The goal of this study is to increase the effective heat conductivity (EHC) of the polymer composite materials. We have carried out numerical simulation of the polymer composite EHC when making microsized high-thermal conductivity fillers of various shape a component of the composite, and its volume fraction being varied форas well. The influence of particles’ thermal conductivity on the polymer composite materials’ EHC was analyzed. Recommended practice for the polymer composite EHC increasing was suggested. Shape changing, volume fraction optimization, the filler particles’, and the matrix’ thermal conductivity increasing was proposed. The calculation results were in good agreement with our experimental data and published in scientific literature. This study gave an insight into the function of high-thermal conductivity fillers on the EHC of the polymer composite materials.