The invention provides a continuous variable transmission with a downhill braking function. The continuous variable speed transmission comprises supports, a driving fixed belt pulley set, a braking device and a driving moving belt pulley set, the driving fixed belt pulley set is fixedly installed at one end of a driving fixing shaft, the driving moving belt pulley set is slidably installed at the other end of the driving fixing shaft, the outer end of the driving moving belt pulley set and the tail end of the driving fixing shaft are fixedly provided with the supports in a screwing mode through hexagon nuts, the braking device is installed on the driving fixing shaft between the driving fixed belt pulley set and the driving moving belt pulley set, and comprises a one-way shaft sleeve fixed by a rolling guide pin, the outer side of the one-way shaft sleeve is sleeved with a sealing sleeve, the outer side of the sealing sleeve is provided with a one-way bearing, and the upper side and the lower side of the one-way bearing are provided with a first thrust washer and a second thrust washer respectively. According to the continuous variable transmission with the downhill braking function, the braking device is installed on the driving fixing shaft, when an engine is in an idling state, the one-way bearing drives the one-way sleeve shaft to rotate, a belt is clamped, the braking effect is exerted, the braking effect is good, and the service life of the belt is prolonged.