In this study, unmodified graphite and graphite modified with a silane agent were used to ameliorate the thermal conductivity coefficient and dynamical properties of unsaturated polyester resin. The effect of unmodified graphite and modified graphite addition on thermal conductivity coefficient and dynamical properties of unsaturated polyester resin in the graphite amounts of 0.02% and 0.3% by weight were studied using solid thermal conductivity measuring device and DMA test. The results showed that the silane modifier can help to create strong covalent bonds between graphite particles and unsaturated polyester resin network and cause changes in thermal and dynamic properties compared to unmodified graphite particles. Adding 0.3% of the weight of the unmodified graphite to the unsaturated polyester resin resulted in a 7% raise in the storage modulus in the glassy region. However, adding the same amount of graphite modified using the silane agent increased the storage module by 33% in the glassy region. Silane modifier caused better dispersion of graphite particles in the resin structure. Superior dispersion of graphite particles caused more interaction between graphite particles and resin network, which significantly increased the modulus of unsaturated polyester resin. In contrast, better dispersion of graphite particles because of the presence of silane agent increased the thermal resistance at the surface of graphite particles, which reduced the thermal conductivity coefficient compared to unmodified graphite.