The invention provides an iron core loss-based direct torque control method for an ultra-high-speed permanent magnet synchronous motor. The invention discloses an iron core loss-based mathematical modeling method for the ultra-high-speed permanent magnet synchronous motor; a voltage equation, a flux linkage equation and a torque equation are adopted in motor rotary speed control by adopting the direct torque control method, wherein the flux linkage value is obtained by three-phase current calculation through a finite element analysis method; and iron core loss is taken into consideration in the voltage equation, and the iron core loss is converted into equivalent resistance. The method disclosed in the invention can be applied to the ultra-high-speed permanent magnet synchronous motor control system based on sensor-less rotary speed estimation; and angular error caused by iron core loss in the sensor-less rotary speed estimation can be effectively lowered.