Transmission system of speed reducer

The invention relates to a transmission system of a speed reducer, and relates to the field of reduction gearboxes, the transmission system comprises a power output mechanism, a power transmission mechanism and a torque adjusting assembly arranged on the power transmission mechanism, the power output mechanism is connected with a motor, the motor drives the power output mechanism to operate, and the power output mechanism drives the power transmission mechanism to operate. The torque adjusting assembly comprises a second friction disc coaxially and slidably arranged on the first transmission shaft in a sleeving mode, a spring pressing disc slidably arranged on the first transmission shaft in a sleeving mode, and an extrusion spring fixedly connected between the second friction disc and the spring pressing disc and used for extruding the second friction disc. The pressure adjusting disc is in threaded connection with the first transmission shaft and used for adjusting the position of the spring pressing disc,