The invention relates to a phase-commutating failure forecasting method applicable to a layered access way. The phase-commutating failure forecasting method comprises the following steps: collecting the direct currents of neutral busses in the pole; judging whether the direct currents meet a phase-commutating failure forecasting criterion, wherein the phase-commutating failure forecasting criterion comprises that the difference between the time when the break variables of the direct currents are greater than a first preset threshold value and the time when the break variables of the direct currents are greater than a second preset threshold value is smaller than a preset time length; and carrying out measures for preventing a phase-commutating failure if the phase-commutating failure forecasting criterion is met. According to the phase-commutating failure forecasting method, the phenomenon of the phase-commutating failure appearing followed by other converter valves of the pole during the phase-commutating failure of one of the converter valves in the pole can be effectively avoided.