In order to solve the problems of the traditional robot reducer, such as manufacturing difficulty, high cost, resulting in high energy consumption of the motor, a novel continuously variable transmission (CVT) for the robots is proposed in this paper. Compared with conventional metal V-belt type CVT, the CVT is mainly composed of epicyclic pulley train. The planetary pulley revolves following the planet carrier, and the belt rotates and moves around a pair of the sun pulleys. Then the belt transfers movement and power to the planet pulley to drive its rotation. The rotation of the planetary pulley is the CVT’s output that we want to obtain. By changing the axial distance of the pair of sun pulleys, the transmission ratio can be changed and then achieve the functions of forward, neutral and reverse. Its transmission principle is introduced and deduced emphatically. Based on the principle analysis, the prototype of the CVT is designed. The multibody dynamic model of the device is established with the aid of software and the dynamic simulation is carried out. Finally, the physical prototype is manufactured to verify the validity of the design.