A sensorless control strategy of a high-speed 315 kW brushless dc (BLDC) motor based on a speed-independent flux linkage function is proposed in this paper. It addresses the two key challenges on the sensorless control of high-speed BLDC motor: proposing a speed-independent flux linkage function to ensure reliable operation in the low-speed range, and presenting correction strategy to provide accurate commutation points in the high-speed range. First, the sensorless detection circuit model of a 315 kW BLDC motor is discussed. The analysis shows that the speed-independent flux linkage function is really suitable for BLDC motor sensorless control strategy in the low-speed range. Then, an improved closed-loop system based on the change of current in the full speed range is proposed. The experimental results show that the proposed control strategy can provide a highly accurate and robust sensorless operation from near zero to 20 000 r/min.