The invention provides a loop-opening criterion method for channel type electromagnetic looped networks. The loop-opening criterion method includes steps of computing pre-loop-opening indexes and post-loop-opening indexes of the electromagnetic looped networks; constructing evaluation matrixes from the pre-loop-opening indexes and post-loop-opening indexes of the electromagnetic looped networks; carrying out standard processing on the evaluation matrixes to obtain standard matrixes; computing various index weights by the aid of variation coefficient processes to obtain pre-effect indexes and post-effect indexes; judging whether loop-opening is carried out or not according to the pre-effect indexes and the post-effect indexes. The loop-opening criterion method has the advantages that comprehensive loop-opening and loop-closing index systems for the channel type electromagnetic looped networks are constructed, and accordingly the loop-opening necessity can be judged.