In order to strengthen the sealing at the small clearance of the stator-based dual air-cooled external rotor permanent magnet synchronous motor and ensuring the heat dissipation of the clearance,the numerical simulations of the flow field and heat transfer characteristics of the small clearance of the motor with different labyrinth sealing structures under different working conditions were carried out by using computational fluid dynamics,taking into account the rotational factor.The influences of different labyrinth sealing structures at the upper and lower clearance on the overall sealing performance of the motor and the heat dissipation of the stator sidewalls were explored by analyzing the pressure and velocity at the clearance.The sealing performance and heat dissipation were evaluated using leakage and Nusselt number as evaluation factors.The results show that when the axial fan operates with suction,it is more conducive to improving the sealing performance of the motor and ensuring the heat dissipation at the clearance.Adding labyrinth seals at the upper and lower stator clearances can effectively improve the sealing performance of the motor in the dual air-cooled system,and the greater the total pressure drop of the sealing structure at the upper and lower clearances,the smaller the leakage.The average Nussell number of the stator sidewall at the clearance will decrease due to the addition of the labyrinth seal.When the incoming temperature is lower than the wall temperature,the extent of decrease of average Nussell number will increase with the increase of the flow-blocking effect of the sealing structure,and when the incoming temperature is higher than the wall temperature,the extent of decrease of average Nussell number will increase with the decrease of the flow-blocking effect and the notch vortex strength.Compared to the unsealed structure,the stator side double groove structure effectively ensures the heat dissipation of the clearances while improving the overall sealing performance of the motor.The research results provide a reference for the design of the sealing and heat dissipation structure at the internal clearances of the external rotor permanent magnet synchronous motor.