In this paper, the three straight casing tubes and the double helix casing tubes were modeled using the Gambit software. And the fluid flowing in tubes was simulated by Fluent software. According to the simulation results, with the field synergy principle, two casing tubes’ flow and temperature distribution of carbon dioxide and water have been analyzed. Simulation data show that the double helix casing tubes is better than the three straight casing tubes on heat transfer and synergy. Lay the good foundation for design optimization and efficiency of heat exchanger of carbon dioxide heat pump system.