The invention relates to a standby link discovery realization method based on three-layer network routing. The method comprises steps that, S1, a set P1 is formed according to port information of discovery service acquisition equipment of the three-layer network routing; S2, port information possibly having a link relation is filtered from the set P1 according to first rules to form a set P2; S3, whether the set P1 and the set P2 satisfy second rules are sequentially analyzed; if yes, port IP is generated into link information to form a new link, the process enters a S4, and if not, the process enters a S5; S4, whether newly-generated links exist in a link table in the prior art is determined, the new links are marked as standby links, and the progress enters the S5; and S5, whether IP of all ports of the set P2 are analyzed through the second rules is determined. The method solves a problem that topology based on the three-layer network routing table can not discover the standby links, and provides guarantee for discovering the integral network topology.