The present invention relates to a computer system capable of adjusting the operating frequency dynamically and comprises at least a processor voltage-adjusting unit, a clock-generating circuit, at least a load-detecting unit, and a control unit. The processor voltage-adjusting unit and the clock-generating circuit produce a processor operating voltage and a clock signal, respectively, and transmit them to the processor. The load-detecting unit detects the processor for producing a detecting signal related to the load of the processor. The control unit produces a clock-adjusting signal and a processor voltage-adjusting signal according to the detecting signal and controls the processor voltage-adjusting unit and the clock-generating circuit, respectively. Thereby, the control unit can adjust the operating voltage of the processor as well as the frequency of the clock signal and hence adjusting the operating frequency of the processor. According, the purpose of adjusting the performance of the computer system dynamically can be achieved.