Abstract: An automatically compressing and friction-driven speed reduction device including a central shaft that is a cylinder, a planet wheel in a disc shape, and an inner compression ring and an outer compression ring sleeved outside the planet wheel; the maximum circumference part of the planet wheel is a planar excircle, and the surfaces on the two sides are machined into inclined planes having certain obliqueness; a planet shaft is installed in the middle of the planet wheel, and fixed on a housing; the planet shaft and the planet wheel are provided with a rolling needle therebetween. The device can automatically adjust frictional pressure in real time according to the magnitude of load torque, thus greatly reducing friction loss, improving the efficiency of friction-driven speed reduction device, and prolonging the service life of the friction-driven speed reduction device.