A duty cycle adjustment apparatus comprises a first edge extraction unit for extracting a rising edge of a first clock signal; a locking discrimination unit configured to output a control signal according to a comparison result between a discrimination voltage and a stabilized voltage, and select to connect the first clock signal or the clock output signal; an integration unit, configured to convert the feedback signal into the stabilized voltage, amplify the stabilized voltage to reach a reference voltage, and output a control voltage; a charge pump, configured to output a second clock signal according to the control voltage; a second edge extraction unit, configured to extract a falling edge of the second clock signal; and a phase discriminator, configured to compare a phase of the rising edge of the first clock signal with a phase of the falling edge of the second clock signal to generate the clock output signal.