A control device for a servo motor system is provided. The control device includes a segment parameter storage circuit, a velocity superposing circuit, a velocity transferring circuit and a pulse comparison circuit. The segment parameter storage circuit is electrically connected with the velocity superposing circuit and the pulse comparison circuit. The velocity transferring circuit is connected between the velocity superposing circuit and the pulse comparison circuit. The velocity superposing circuit updates a present velocity value according to a target velocity value and an increment. The velocity transferring circuit generates a PWM signal according to the present velocity value. The pulse comparison circuit transfers the PWM signal into a signal of a command pulse wave group and judges whether a pulse number of the PWM signal reaches a predetermined pulse number.