The invention discloses a shared-frequency asynchronous phase-checking method and belongs to the field of measurement. The method comprises the following steps of: generating a synchronous standard phase signal serving as a third-party reference by means of a commercial power network; sequentially acquiring a voltage phase signal between each phase of a system power supply and each corresponding phase of the to-be-checked power supply; performing phase comparison on the measured voltage phase signal and the third-party reference at the time to obtain a voltage phase differential value; comparing the voltage phase differential value between each phase of the system power supply and each corresponding phase of the to-be-checked power supply to obtain a comparison phase difference; and judging whether each phase of the system power supply and each corresponding phase of the to-be-phased power supply belong to the same phase or not according to the value range of the phase difference so as to obtain the conclusion whether the system power supply has the same phase as the to-be-phased power supply or not. The asynchronous phase-checking method can check phases of systems with the same or different voltage levels, can test whether a power supply loop has the failures, such as 'phase failure' and the like, or not, can check phases in different places and widens the application field of the routine phase-checking tests.