A variable speed fan motor, including: a variable speed motor and a motor controller. The motor controller includes a microprocessor, an inverter circuit, a gear detection circuit, and a power supply unit. The gear detection circuit includes a plurality of Hall current sensing units. Each second power input line is connected with a first input end of each of the Hall current sensing units. Second input ends of the Hall current sensing units are connected in parallel, and are connected with a second AC input end of the power supply unit. An output end of the Hall current sensing unit is connected with an input end of the microprocessor. The microprocessor selects operating parameters according to an energized signal of the second power input lines and controls the variable speed motor to operate in accordance with the selected operating parameters.