Electrical stimulation technology has significant application value in clinical rehabilitation of motor function, and the development of advanced electrical stimulation systems is crucial for achieving precise and efficient neuromuscular electrical stimulation. This work combines digital signal synthesis and a constant current source circuit model to design a multi parameter adjustable electrical stimulation system with small output current error. The system can output three waveforms: square wave, triangular wave, and sine wave. The output current error is less than 0.5%, and the maximum output impedance is 4 000 Ω. The frequency error in the range of 10~500 Hz is less than 0.5% for square wave, less than 1% for triangular wave, and less than 3% for sine wave. Compared with KT-90A and PE1-2 medical grade electric stimulators, the system still maintains high current accuracy at a minimum output impedance of 2 000 Ω, and the waveform is not distorted. The system was applied to neuromuscular functional electrical stimulation experiments, and the effectiveness of the system in clinical rehabilitation applications was verified by analyzing the waveform and energy spectrum of EEG waves. This work is expected to provide technical support for the clinical application of electrical stimulation rehabilitation intervention.