Abstract: A circuit and method for driving a magnetostriction oscillator which is used for generating a high output ultrasonic wave by using a pulse width modulation is provided. In the circuit, a controller outputs first and second variable digital signals in order to control a duty cycle of a magnetostriction oscillator. A pulse width modulating circuit generates a variable pulse width modulating signal based on the first and second variable digital signals from the controller. A driver drives the magnetostriction oscillator according to the variable pulse width modulating signal from the pulse width modulating circuit. According to the circuit, the system operates for a long time so that stability of equipment can be obtained. The circuit uses low voltage and low energy so that efficiency of the system is promoted.