The invention discloses a motor pulley of an oil pumping machine, and a mounting method, and belongs to the technical field of machinery. According to the motor pulley of the oil pumping machine, a baffle is connected with a base gear through baffle bolts, an outer gear is meshed with the base gear through tooth grooves, and a lug boss is formed at one end of the base gear. The base gear is directly mounted on a motor bearing, as a common belt pulley, the base gear with a key generates a self-locking function by utilizing a shaft with a taper, so that the base gear is prevented from separating from a motor shaft; the outer gear is meshed with the base gear through the tooth grooves, so that the outer gear can be dismounted or mounted only by hands or simple tools; the lug boss is designed at one end, close to a motor, of the base gear, and the baffle is designed at the outer end of the base gear, so that the base gear can be prevented from separating from the outer gear under the working state. According to the motor pulley disclosed by the invention, the integral structure of a conventional belt pulley is improved into a split combined structure, after the motor pulley is mounted, the base gear does not need to be dismounted when regulating the frequency of strokes unless the motor needs to be replaced, and besides, because the outer gear is meshed with the base gear through teeth and grooves, self-locking does not happen.