An operation monitor device for a hardware component detects a load current that is changed due to the operation of the hardware component through a pulse width modulation (PWM) module; thereby generating a voltage variation. A monitoring unit outputs a detecting result to a system by detecting the voltage variation and generates a modulating signal in response to a monitor signal fed back by the system according to the detecting result, such that a controller generates a reference voltage variation according to the modulating signal. In this way, the load current changes as the load of the hardware component increases, such that the controller changes the generated reference voltage and further modulates the output voltage supplied to the hardware component by the PWM module, thus meeting the execution state of the hardware component and improving performance.
