The development of heavy icebreakers above PC2 class has become an important part of the polar strategy with the growth of the demand of polar exploration research and development in China. A propulsion system with great power and redundancy is a particular feature of heavy icebreakers. It is found that the electric propulsion system has become the development trend through the analysis of the foreign heavy icebreakers using conventional power. The total capacity of its integrated power system is often greater than 50 MW. The output power of the propulsion motor can reach 20 MW with multiple main thrusters, and the single engine power may exceed 10 MW with more than four prime motors. The capacity level of the above-mentioned key devices of the power system is rarely used on existing ships, with insufficient domestic supporting parts. The essential parts of the power system such as the generators, propulsion motors and frequency converters are selected by analyzing the power grid voltage level based on the demand of heavy icebreakers. Combined with the domestic supporting situations, a power grid architecture for the heavy icebreaker is proposed with reference to the existing power grid architecture in foreign countries, in order to facilitate the development of subsequent ships.