The Northern Sea Route is a new way to connect Asia and Europe. To utilize the sea route, merchant ships are required to have the icebreaking capability. Since conventional fossil fuel engines have limitations for the icebreaking merchant ship propulsion, nuclear power having a long refueling period for icebreaking merchant ship is proposed in this paper. To evaluate the technical feasibility of the nuclear power for the icebreaking ship's engine, 330MWth SMART is selected for the reference reactor core. The power conversion system for the SMART core is substituted with the trans-critical CO2 recompression cycle that has advantageous in low-temperature heat sink as in Northern Sea Route and low-temperature heat source, Pressurized Water Reactor operating conditions. In this paper, the major components of the trans-critical CO2 cycle are designed. Then, CO2 PRHRS, which is driven by CO2 natural circulation loop, is designed to substitute steam-water based PRHRS.