The ever increasing popularity of electric vehicles and higher requirement on safety and comfort has led heat pump air conditioning system indispensable in electric vehicle. Many studies have shown that the addition of nano particles contributes to great improvement on thermal conductivity than that of conventional refrigerants. Therefore, the application of the magnetic nanorefrigerant in heat pump air conditioning system has massive potential to heighten the heat transfer efficiency. This paper aims at studying the magnetic nanorefrigerant comprised of the magnetic nano powder Fe3O4 and refrigerant R134a. According to the relevant theoretical analyses and empirical formula, the heat transfer coefficient, density, viscosity, and other physical parameters are calculated approximately. In the heat pump air conditioning system of a certain type of electric vehicle, the special working condition parameters are selected to carry out calculation analysis with numerical analysis software. The results show that the heat exchange amount of this nanorefrigerant is 21.23% higher than the pure refrigerant R134a and increases with the volume fraction of the nano particles. Moreover, after adding Fe3O4 nano materials to the heat pump air conditioning system, the efficiency of this system has been increased by 8.6%. So the conclusion can be drawn that appliance of the nano-refrigerant in electric vehicle is both effective and feasible.