The invention discloses a speed reduction transmission device. By means of the speed reduction transmission device, speed reduction transmission can be effectively carried out, the overall structure is reasonable, the matching accuracy is high, running is stable, and it can be guaranteed that the instant position fluctuations of all structures are small and errors and accumulative errors are fewer, and the transmission accuracy can be effectively guaranteed. The speed reduction transmission device comprises a tank body, a power motor, an upper worm, a lower worm and a transmission worm gear; and the upper worm and the lower worm are provided with an upper gear and a lower gear respectively, the lower worm is connected with the power motor, the upper worm and the lower worm are connected with the transmission worm gear in a matched manner, the upper gear and the lower gear are located outside the tank body, and the upper gear is meshed with the lower gear. Helical teeth of the upper worm and helical teeth of the lower worm are the same in tooth shape, the lower worm gear comprises a worm gear shaft and a sliding sleeve, the helical teeth of the lower worm are located on the sliding sleeve, and the sliding sleeve is in sliding connection with the worm shaft; and the worm shaft is provided with a limiting neck, a compensation gap is reserved between one end of the sliding sleeve and the limiting neck, and the other end of the sliding sleeve is pressed by a self-adjusting spring.