Journal of Electronic Systems Meizhi Zhang 6 4 2016 http://www.dline.info/jes/fulltext/v6n4/jesv6n4_2.pdf This study deduced a set of theory computational formula, and optimized and improved the heat-conductivity of vias in printed circuit board (PCB) of electrical power apparatus. We adopted numerical simulation and experimental measurement to verify the reliability of this formula. Through the theory computational formula, this paper studied the influence of aperture of vias, filled materials and thickness of copper plated on vias on thermal conductivity. Research result showed that 0.45mm was the optimal diameter of bore of vias; the conductivity had no obvious improvement when filling material was FR4 or Rogers, but if it was filled with texture of high thermal conductivity like soldering tine, the conductivity would improved a lot; the plating thickness of vias had greater influence on thermal conductivity. The adoption of three optimization scheme of vias recommended by the result could respectively improve 6.5%, 35% and 51% of thermal conductivity.