The invention provides a method and a device for controlling the thickness of a finished product of a motor silicon steel sheet, belonging to the technical field of motors. The invention solves the problems that the thickness of the finished product of the motor silicon steel sheet is manually measured by rulers, and the materials are wasted in the prior art. The method for controlling the thickness of the finished product of the motor silicon steel sheet comprises the following steps of: A, measuring the weight of a standard component; B, measuring the thickness; C, processing data; and D, controlling the thickness. The device for detecting the thickness of the finished product of the motor silicon steel sheet comprises a bracket, ranging sensors and a controller, wherein the bracket is arranged on a cut of a cutting machine; the ranging sensors are arranged on the bracket, the controller is used for receiving signals of the ranging sensors, processing the received signals and outputting control signals; the two ranging sensors are connected with an input interface of the controller respectively; and the output interface of the controller is connected with a signal processing module which is used for controlling the cutting machine to cut. According to the method and the device, the thickness of the finished product of the motor silicon steel sheet can be automatically controlled, so that the method and the device can be applied to automatic production lines, the production efficiency is improved, and the waste of materials is reduced.