Solar power system that can get directly from the natural eco-friendly and, without causing pollution is a static work device. In addition, ease of maintenance because recently a lot of technical development is being done. Solar power system solar cells without the help of a generator by converting sun power directly into electrical energy is developed by using solar power to DC Power Conditioner Unit(PCU) through a AC power or converted into DC power, residential, business, and many places are supplied to the load. In this paper, 3kW-class thermal and flow distribution inside the inverter ICEPAK numerical analysis using commercial packages was carried out. PCU"s main heat sources inside the Igbt, Reactor, Capacitor, and pars by the heat of the malfunctioning parts, components and parts life, and many have a problem, because the thermal PCU internal temperature should be managed. PCU for the optimal design of numerical analysis of various cases were in progress, leading to designers through a variety of numerical information given was incorporated into the design. In particular, depending on whether the internal fan was install or not the temperature of the internal flow varried up to 4 degrees, the capacitor"s temperature showed a maximum difference of 20 degrees, capacitors, cooling and circulation of internal flow and the fans should choose the appropriate order.