Brushless DC motors (BLDCM) are widely used in aerospace and other control fields due to their advantages of long life, high power density, small size, and large output torque. However, the traditional method of using the sensor to obtain the rotor position signal has the disadvantages of difficulty in manufacturing, susceptibility to interference, and difficulty in working in high and low temperature environments, which greatly limits its wider application. Sensorless control technology can overcome these shortcomings. This article introduces the back-EMF method, state observer method, and artificial intelligence method for sensorless brushless DC motor control. In view of the problem that the back-EMF method cannot be started at zero or low speed, rotor position detection method and how to accelerate to closed-loop state control scheme are also introduced.