The invention provides a single-pedal speed control system of an electric vehicle. The single-pedal speed control system comprises a speed control pedal, a pedal position sensor, a speed controller, a brake valve and a return spring. The single-pedal speed control system has the advantages that starting, accelerating, decelerating and braking of the electric vehicle can be controlled by the speed control system according to the position of the pedal and current states of a motor, braking releasing, motor power-on, motor accelerating and motor power-off procedures are sequentially carried out when the pedal is released, motor rotation speed reducing, motor power-off and braking procedures are sequentially carried out when the pedal is treaded, and accordingly different deceleration requirements can be met; starting, motor rotation speed regulating and state switching can be automatically completed by the aid of the controller according to operation on the pedal, and accordingly the driving convenience and safety can be improved; problems of high operational complexity and easiness in causing misoperation due to the fact that an existing acceleration pedal and an existing brake pedal are separately arranged can be solved by the aid of the single-pedal speed control system.