The invention provides a method and device for automatically adjusting a phase sequence. The method comprises the following steps of 1) detecting a phase sequence of an inverter input three-phase AC voltage before a device is put into operation; 2) achieving phase locking according to a phase sequence of A, B and C, and controlling an inverter to start and run; and 3) automatically adjusting phaselocking when the phase sequence is not correct, achieving phase locking according to a phase sequence of A, C and B, and controlling the inverter to start and run according to the phase sequence of A, C and B. By the method, the problems of complicated self-adaptive adjustment process of the phase sequence and time delay in the adjustment process are solved.