A device for measuring speed of a belt conveyer scale of a coal feeder belongs to the technical field of measurement equipment, and is used for measuring running speed of the belt conveyer scale of the coal feeder synchronously. The device adopts the technical scheme that the device consists of a driving gear, a driven gear, a driven gear support, a speed measurement encoder and a dustproof cover, wherein the driving gear is sheathed on an output shaft of a speed reducer; the driven gear is meshed with the driving gear; the driven gear and the driving gear have the same number of gears and modules; the two ends of the driven gear are installed on the driven gear support; a rotating shaft of the speed measurement encoder is fixedly connected with a driven gear shaft; and the speed measurement encoder is installed in the dustproof cover. Through the drive of the driven gear and the driving gear, the speed measured by the speed measurement encoder is the speed of a belt conveyer roller, so as to ensure the synchrony and the accuracy of the speed measurement; and the speed measurement encoder is arranged outside a host to avoid influence from the poor work environment and damage. The device provided by the utility model has the advantages of convenience in use and maintenance, low cost, high accuracy and high efficiency.