Method for controlling the rotating speed of an electromechanical device is disclosed herein, the aforementioned method including the following steps. The first step is to map a plurality sets of electrical-parameter means to different ranges of rotating speed of the electromechanical device to form a mapping table. The plurality sets of electrical-parameter means couples various resistance to the electromechanical device and eliminating the back EMF (Electro-Mechanical Force) in said electromechanical device. The second step is to connect a set of electrical-parameter means of said plurality sets of electrical-parameter means to a driving means. The driving means is used to provide the power that used in the operation of the electromechanical device, the set of electrical-parameter means is connected to the driving means according to the mapping table.