The invention discloses a method for identifying line breaking of a power supply line and switching to a standby power supply. The method comprises the following steps: acquiring on-off signals of a power supply switch and a standby power supply switch and voltage signals output by load bus voltage measurement equipment, current signals output by current measurement equipment at the power supply switch and voltage signal data output by voltage measurement equipment at other sides of electrically interconnected equipment, and performing determination on the acquired signals. According to the invention, based on a conventional standby power supply switching apparatus, through additionally monitoring whether currents on a power supply three-phase line disappear and whether voltage signals at secondary output ends of voltage transformers at other sides of load buses and the electrically interconnected equipment reflect that three-phase voltage unbalance values are greater than specified values, integrated determination is performed, such that determination of line breaking of the power supply line is improved, and whether in case of complete power failure or single-phase and two-phase power shortages caused by single-phase, two-phase or three-phase line breaking of the power supply line, or abnormal power supply of an original power source, caused by other faults, a standby automatic switching apparatus can timely switch off the power supply switch to prevent the equipment from damage and automatically switch on the standby power supply switch to ensure continuous normal power supply.