The invention discloses a controller for electric bicycles and motorcycles. The controller comprises a voltage-stabilized power circuit, a PWM (pulse width modulation) generation circuit, a motor drive circuit, a motor overcurrent protection circuit, a battery overdischarge protection circuit, and a battery discharge indicator circuit. The voltage-stabilized power circuit and the PWM generation circuit are connected with each other. The output end of the PWM generation circuit is connected with the input end of the motor drive circuit, the input end of the motor overcurrent protection circuit, the input end of the battery overdischarge protection circuit, and the input end of the battery discharge indicator circuit. The PWM generation circuit comprises a pulse width modulator and a potentiometer. The motor drive circuit comprises a VDMOS transistor and a permanent magnet direct-current brush motor. The battery discharge indicator circuit comprises five LED display lamps and a four-OA (operational amplifier) integrated circuit formed by parallelly connecting four LM324 comparators. The controller for electric bicycles and motorcycles has the functions of battery undervoltage protection, motor overcurrent protection, brake outage, electricity displaying and the like, and is simple in structure and low in cost.