A phase sequence adjustment system includes a power conversion circuit and a control circuit. The power conversion circuit is connected to a main power supply with a phase sequence. The control circuit respectively provides a first and a second excitation signals to the power conversion circuit, so as to short the power conversion circuit with the main power supply twice. The control circuit includes a current detection circuit and a control unit. The current detection circuit obtains two current signals respectively during two short-circuit operations. The control unit calculates two current phase angles respectively according to these two current signals and determines whether the phase sequence is positive or negative accordingly. The control unit selects one from the two current phase angles, calculates a voltage phase angle of the main power and a phase angle difference there-between to adjust a feedback phase sequence accordingly.