Speed reduction device and hub-driven vertical roller mill applying speed reduction device

The invention provides a speed reduction device and a hub-driven vertical roller mill applying the speed reduction device, a first planet carrier of a first planetary transmission stage is fixedly connected with a grinding roller and outputs power to the grinding roller, a first inner gear ring outputs power to a second sun gear of a second planetary transmission stage, the second sun gear drives the second inner gear ring to rotate, and the second inner gear ring drives the grinding roller to rotate. And the second inner gear ring outputs the power to the grinding roller. The first planetary transmission stage and the second planetary transmission stage transmit power to the grinding roller at the same time, large torque can be guaranteed while the transmission efficiency is improved, and the structure is more compact. A plurality of motors and speed reducers with lower single-machine installed power and torque are adopted, an original main speed reducer is omitted, and the problem that the speed reducers ar