Permanent magnet synchronous motor (PMSM) is compact and has high-power density. Heat dissipation conditions introduce new challenges and opportunities for further improvement of its power, efficiency, and reliability. In this article, a jet cooling method was proposed. The feasibility of jet cooling method was studied by taking a 600 kW PMSM as a prototype. Based on the Euler two-phase model, the effect of thermal performance was numerically studied, varying different inlet velocity, inlet liquid volume fraction, and jet cone angle. Also, the influence of the revolution speed and number of nozzles on the cooling effect was analyzed. The distribution of temperature and liquid phase was discussed. The numerical results illustrate that the maximum temperature of PMSM is only 370 K, which proves the heat dissipation capacity of the cooling system. At the air gap entrance, the temperature and liquid phase are distributed periodically. Under standard conditions, three nozzles, inlet velocity of 60 m/s, and 0.3 inlet liquid volume fraction can achieve high efficiency cooling. Heat dissipation depends largely on liquid. The cooling effect is enhanced by increasing the inlet liquid volume fraction. The optimal jet cone angle is 0 deg, which allows more liquid phase to enter the air gap. At high rotational speed, to avoid hindering the liquid phase from entering the air gap, the inlet velocity should not be less than 60 m/s.