Abstract: A transmission speed reduction device, comprising: a worm assembly (1) which is located within a container body (2), a worm wheel assembly (3) and an output axle (4); an input axle (11) is provided on the worm assembly (1), while the worm assembly (1) and the worm wheel assembly (3) achieve primary stage mesh transmission there between by means of worm teeth which are provided on the worm assembly (1) and a first worm wheel tooth (34) which is provided on the worm wheel assembly (3); the worm wheel assembly (3) and the output axle (4) achieve secondary stage mesh transmission by means of an intermediate rotary body (32) which is provided on the worm wheel assembly (3) and a rotary disc assembly (5) which is fixed on the output axle (4).