In electronic products, the recently increasing thermal radiation demands higher thermal conductivity of polymer composites. However, inaccurate observation of the filler dispersion within the polymer does not allow for accurate quantification of Interface Thermal Resistance and subsequently the prediction of thermal conductivity. Therefore, optimum filler design could not be achieved.Firstly in this report, accurate stereoscopic filler dispersion was observed by FIB-SEM. Secondly, quantification of Interface Thermal Resistance could be achieved by thermal conduction analysis using filler dispersion model. Thirdly, this Interface Thermal Resistance enabled the prediction of the thermal bulk conductivity. Lastly, the prediction made above could be validated by comparison of predicted value to measured value.This result may lead to optimum filler design and thereby to the development of higher thermal radiation materials.