A processor frequency adjustment circuit for adjusting a frequency of a processor includes a voltage converting module, a first reference voltage generating module, a clock chip, a voltage comparing module. The voltage converting module converts a pulse voltage into a constant voltage. The first reference voltage generating module generates a first reference voltage. The voltage comparing module is connected with the voltage converting module, the first reference voltage generating module, and the clock chip to compare the constant voltage with the first reference voltage, and generates a first voltage level signal to a first terminal of the clock chip; the clock chip adjusts the frequency of the processor in response to obtaining the first voltage level signal.