A motor controller, including: a microprocessor including a signal identification unit; an inverter circuit; a rotation speed detection circuit; a power module; and an isolation circuit. The power module supplies power for the microprocessor, the inverter circuit, the rotation speed detection circuit, and the isolation circuit. The isolation circuit is connected to the microprocessor via a pulse width modulation (PWM) input line, and a PWM signal is transmitted to the isolation circuit and the microprocessor successively via the PWM input line. One rotation speed input signal of a motor is transmitted to the signal identification unit of the microprocessor via the isolation circuit and the PWM input line. The signal identification unit determines whether an input signal of the PWM input line is the PWM signal or the one rotation speed input signal of the motor.