The invention teaches a speed control system for a brushless DC motor for a ceiling fan, comprising a power circuit 1, a microprocessor circuit 2, a power drive circuit 3, a speed regulation circuit, and a brushless DC permanent magnetic motor 5, wherein the input terminal of the power circuit 1 is connected to the output terminal 101 of an AC power source, the output terminal of the power circuit 1 serves to power the various circuits, the output terminal of the microprocessor circuit 2 is connected to the input terminal of the power drive circuit 3, the output terminal of the power drive circuit 3 is connected to the coil windings 501 of the brushless DC permanent magnetic motor, and the output terminal of the speed regulation circuit is connected to the input terminal of the microprocessor circuit 2. The speed control system of the invention provides the advantages of low energy consumption, low noise during the operation of the motor, and a stable operation at low speeds.