New electric molding composites were fabricated with hybridizing epoxy and several fillers. The examined fillers were β-Si3N4, BN and fused silica or their combinations. The thermal conductivity of β-Si3N4 filler was compared with BN as filler for advanced epoxy molding compounds. The influence of pure resin matrix and mixture matrix on the thermal conductivity of EMC was discussed. The results were explained with Maxwell equation.