The invention discloses a bus protecting method based on the relevancy of virtual electric currents, and belongs to the technical field of electric power systems and automation thereof. The bus protecting method disclosed by the invention comprises the following steps: performing sampling on each branch according to a fixed sampling interval; performing rolling integral processing on the sampled current value of each branch at each sampling point, wherein the processing results are used as a basis for judging the polarity of the branch current; combining sampled values obtained at the same time so as to simplify the multi-branch bus system into a simple bus which only has virtual currents flowing in and out; continuously calculating the relevancy of waveforms of virtual currents by utilizing short data windows according to the characteristic difference of the waveforms of virtual currents under different running states of the bus, and distinguishing internal and external faults of bus areas according to the distributing situation of values according to the multi-point relevancy. Through the adoption of the bus protecting method disclosed by the invention, the internal and external faults of bus areas can be quickly and reliably judged without being influenced by the fault types or the transition resistance of faults; the bus protecting method is resistant to TA saturation and frequency deviation, so that the accuracy and the rapidity of action are improved.