Functional Electrical Stimulation (FES) has already been used in many aspects of rehabilitation medicine as a treatment method. According to the functional electrical stimulation, we present an electrical muscle simulator which can adjust the amplitude, frequency and wave of electrical impulses by button and make the treatment more effective. In this paper, we will introduce the basic principle of the functional electrical stimulation and the basic parameters of stimulation waveform, as well as we will present a framework of this device. There are two crucial components should be elaborately designed, the hardware system and the software system. Moreover, the analysis of the electrical signal is mentioned in this paper last.