Abstract: In order to meet the tenderizing requirements for different varieties and parts of the beef, an electrical stimulation instrument was designed in this paper. Based on pulse-width modulation (PWM), this instrument was composed of single-chip microcomputer MSP430 and H-bridge with four MOSFET. By controlling the duty cycle of the PWM/SPWM（Sinusoidal PWM） produced by single-chip microcomputer, this instrument could realise the inversion of direct current by H-bridge, and thus generae different wave forms. the functions, operation principles, hardware and software structure of the instrument were introduced in this paper. Test results showed that: the instrument could produce 5 types of the waveforms, namely, DC, square wave, sine wave, triangular wave and sawtooth wave. The parameters of electrical stimulation instrument were all adjustable. The peak voltage range of each waveform was 0-110?V and frequency adjustment range was 1-450 Hz. The output of electrical stimulation parameters can achieve the tenderizing requirements with its high precision, which provides the technical support for the beef tenderizing processing.