An I/Q imbalance calibration method includes sequentially inputting a first in-phase and quadrature signals calibration signal to a front-end circuit of the transmitter system to acquire and estimate a first and second calibration signal strengths sequentially, wherein a delta estimation is adopted; calculating an I/Q gain imbalance according to estimated first and second calibration signal strengths; sequentially inputting a second in-phase calibration signal and both of the second in-phase and quadrature calibration signal to the front-end circuit of the transmitter system to acquire and estimate a third and fourth calibration signal strengths sequentially, wherein an I/Q gain imbalance compensation is formed on the first in-phase and quadrature calibration signals to generate the second in-phase and quadrature calibration signals; and calculating an I/Q phase imbalance according to estimated third and fourth calibration signal strengths.