The invention discloses a method for detecting an optical fiber channel router and aims at solving the technical problem that the accuracy of the optical fiber channel detection is not high. The method comprises the following steps of adjusting sampling time to enable the sampling time on two sides of a line to be synchronous; sampling voltage and current, performing analog-digital conversion, calculating onside phase voltage vectors, onside phase current vectors and offside phase voltage vectors and calculating onside positive sequence voltage vectors and current vectors and offside positive sequence voltage vectors; calculating offside converted positive sequence voltage vectors; comparing phase positions of the offside positive sequence voltage vectors and phase positions of the offside converted positive sequence voltage vectors, if the phase positions are identical, optical fiber channels are judged to be identical. Compared with the prior art, a host machine and a slave machine respectively synchronize the sampling time on the two sides, offside data are transmitted to the onside after sampling, the offside positive sequence voltage vectors and the positive sequence voltage vectors are calculated and compared, whether optical fiber channels in operation are identical or not is judged, and the reliability of differential protection is improved.