A calibration circuit and a calibration method are provided. The calibration circuit has a delay circuit, a phase detector, and a controller. The delay circuit delays an input signal to output an output signal, wherein a delay time between the input signal and the output signal is related to an equivalent capacitance and an equivalent resistance of the delay circuit. The phase detector coupled to the delay circuit compares the phases of the input signal and the output signal. The controller coupled to the delay circuit and the phase detector generates a control signal according to the comparison result of the phase detector to adjust the equivalent resistance of the delay circuit.