The invention discloses a method for controlling the speed of a lifting belt of a feeding machine and a material transmission system. The material transmission system comprises the feeding machine, the lifting belt of the feeding machine, a metering tube, and an electronic belt balance; the metering tube comprises a first marking element and a second marking element; when a material reaches the second marking element from the first marking element, the speed of the lifting belt of the feeding machine is adjusted by a transducer; the speed of the lifting belt of the feeding machine is in direct proportion to the frequency of the transducer; and the frequency f of the transducer is equal to kQ and is equal to 50(Hz)/largest flow (kg/h)Q of the belt balance. In order to control the material still in the middle position of the metering tube, the method also comprises a step of micro-adjusting the speed of the lifting belt. The method carries out self-adaptive control on the speed of the lifting belt of the feeding machine, can basically keep the speed of the lifting belt in uniform speed, avoids harm to a mechanical part of the lifting belt caused by wide fluctuation of the speed, and also reduces energy consumption. The method controls the material still in the middle position of the metering tube, and can stabilize the density of the material, thereby improving the precision of adding spice and blending.