The invention discloses an electric power communication service routing assignment method based on service importance. The method comprises the following steps of: S1, performing network simplification for an electric power communication routing network, setting a source node and a target node, seeking K paths according to different circuit transmission paths, and setting corresponding importance for each path, wherein K is not less than 1; S2, obtaining a logic mapping matrix G and a threshold value TH according to an electric power communication routing network reliability analysis model; S3, seeking a complete set CS and a touch set TS according to the logic mapping matrix G and the threshold value TH; S4, substituting node reliability with service node risk degree, meanwhile, substituting edge reliability with service path risk degree, finally, calculating a numerical value of reliability, and thereby obtaining an optimal path of the electric power communication routing network.