In this paper, we have studied a novel continuously variable transmission (CVT), which has the potential to be applied to robotics. The transmission principle of the CVT is based on Vbelt transmission and planetary gear train transmission to get large reduction ratio, and its design motivation employs the theory of nested structure to realize a compact CVT. Next, we carry out dynamic simulation on the CVT with different loads and different transmission ratios to analyze work efficiency, and then analyze the dynamics of the planet carrier under the constant torque input. Finally, we develop a prototype with hydraulic drive to adjust the transmission ratio, and design a V-belt composed of multiple metal sheets that can be pre-tightened.