A method for associating a network service (NS) with a virtualized network function (VNF), an apparatus, and a system such that a network manager (NM) can determine a relationship between an NS and a VNF, and maintain the NS. The method includes sending, by an NM, an NS instantiation request message to a network function virtualization orchestrator (NFVO), receiving an NS instantiation completion message from the NFVO, and determining a mapping relationship between a first NS and N VNFs according to information about the first NS and information about the N VNFs. The NS instantiation request message carries the information about the first NS, the NS instantiation completion message carries the information about the first NS and the information about the N VNFs, information about each VNF in the information about the N VNFs represents the VNF in the N VNFs forming the first NS, and N≧1.