The invention discloses an online discrimination method and system for the wrong wiring of a three-phase three-wire metering device, and the method comprises the steps: measuring line voltage effective values, line voltage phase sequences, phase current effective values, phase current phase sequences, reactive power and power factors of a first element and a second element in the three-phase three-wire metering device according to a power utilization collection system; judging the wiring of the metering device according to the line voltage effective values, line voltage phase sequences, phasecurrent effective values, phase current phase sequences, reactive power and power factors of the first element and the second element, and recognizing the wrong wiring in the metering device. The beneficial effects of the invention are that the method achieves the online discrimination of the wrong wiring of the three-phase three-wire metering device based on a conventional power utilization information collection system, so as to achieve the intelligent discrimination of the wrong wiring, and reduce the workload and safety risk of onsite verification.