The ever increasing popularity of electric vehicles and demand in passengers comfort and safe requirements of vehicle have led more efficient heat pump air conditioning system to an indispensable device in electric vehicle. Many studies have shown that the addition of nano particles contributes to improving the thermal conductivity of nano fluids more than that of conventional refrigerants. Therefore, the appliance of the magnetic nano-refrigerant in heat pump air conditioning system has great potential to improve the heat transfer efficiency. This paper aims at studying the magnetic nano-refrigerant comprised of the magnetic nano powder Fe3O4 and refrigerant R134a.According to the relevant theoretical analysis and different empirical formula, the heat transfer coefficient, density, viscosity, and other physical parameters are calculated approximately. And in the condition of the heat pump air conditioning system of a certain type of electric vehicle, the special working condition parameters are selected to be used in the simulation analysis with numerical analysis software. The results show that the heat exchange amount of this nano-refrigerant is higher than the pure refrigerant R134a and increases with the volume fraction of the nano particles. Moreover, after the addition of Fe3O4 nano materials to the heat pump air conditioning system, the efficiency of this system has been significantly improved. So the conclusion can be drawn that appliance of the nano-refrigerant in electric vehicle is both effective and feasible.