A method for associating a network service (NS) with a virtualized network function (VNF) to enable a network manager (NM) to determine a relationship between the NS and the VNF and maintain the NS. The method includes: sending, by the NM, an NS instantiation request message to a network function virtualization orchestrator (NFVO), where the NS instantiation request message carries information about the NS; receiving, by the NM, an NS instantiation completion message from the NFVO, where the NS instantiation completion message carries the information about the NS and information about N VNFs; and determining a mapping relationship between the NS and the N VNFs according to the information about the NS and the information about the N VNFs, where information about each VNF in the information about the N VNFs represents the VNF in the N VNFs forming the NS, and where N≥one.