A network function virtualization, NFV, system, comprising: a single-domain virtualized network function manager, VNFM belonging to a domain layer; a single-domain virtualized network function, VNF, entity belonging to the domain layer; a virtualized infrastructure manager, VIM belonging to a virtual resource layer; and one or more network function virtualized single-domain orchestrators, NFV-DOs, which belong to a domain layer and are in one-to-one correspondence with single-domains, wherein the NFV-DOs each comprises a virtualized network function orchestrator, VNFO, and a single-domain resource orchestrator, RO, and the VNFO is configured to manage one or more of the following functions in a single-domain in which the VNFO is located: network service instance, network service life cycle, VNFM instantiation, VNF instantiation, and VNF life cycle; a network function virtualization orchestrator, NFVO belonging to a network service layer; wherein the NFVO comprises a service orchestrator, SO, and a cross-domain resource orchestrator, CDRO; the SO interacts with one or more VNFOs interfaced with the SO, and interacts with an operation support system, OSS, or a business support system, BSS, and is configured to perform one or more of the following cross-domain processes: network service orchestration, network service instance management, network service life cycle management, network service, and VNF instance policy management; and the CDRO in the network service layer interacts with one or more NFV-DOs interfaced with the CDRO in the domain layer and/or interacts with multiple VIMs, and is configured to perform one or more of the following cross-domain processes: resource authentication and management, resource orchestration policy management, and resource monitoring; the VNFO of the single-domain is configured to transmit a resource reservation application upon receiving a VNF instantiation request, and initiate a VNF instantiation request to the VNFM of the single-domain in which the VNFO is located, upon receiving resource reservation information indicating that the resource reservation application is successful; the VNFM is configured to initiating a resource instantiation request to the VIM according to the resource reservation information; the RO is configured to receive the resource reservation application from the VNFO, only when a resource of the single-domain in which the RO is located is insufficient and a cross-domain resource reservation application is required, transmitting the cross-domain resource reservation application to the CDRO, and when the resource of the single-domain in which the RO is located is sufficient, interacts with the VIM to transmit the resource reservation application in the single-domain in which the RO is located to the VIM. a single-domain virtualized network function manager, VNFM belonging to a domain layer; a single-domain virtualized network function, VNF, entity belonging to the domain layer; a virtualized infrastructure manager, VIM belonging to a virtual resource layer; and one or more network function virtualized single-domain orchestrators, NFV-DOs, which belong to a domain layer and are in one-to-one correspondence with single-domains, wherein the NFV-DOs each comprises a virtualized network function orchestrator, VNFO, and a single-domain resource orchestrator, RO, and the VNFO is configured to manage one or more of the following functions in a single-domain in which the VNFO is located: network service instance, network service life cycle, VNFM instantiation, VNF instantiation, and VNF life cycle; a network function virtualization orchestrator, NFVO belonging to a network service layer; wherein the NFVO comprises a service orchestrator, SO, and a cross-domain resource orchestrator, CDRO; the SO interacts with one or more VNFOs interfaced with the SO, and interacts with an operation support system, OSS, or a business support system, BSS, and is configured to perform one or more of the following cross-domain processes: network service orchestration, network service instance management, network service life cycle management, network service, and VNF instance policy management; and the CDRO in the network service layer interacts with one or more NFV-DOs interfaced with the CDRO in the domain layer and/or interacts with multiple VIMs, and is configured to perform one or more of the following cross-domain processes: resource authentication and management, resource orchestration policy management, and resource monitoring; the VNFO of the single-domain is configured to transmit a resource reservation application upon receiving a VNF instantiation request, and initiate a VNF instantiation request to the VNFM of the single-domain in which the VNFO is located, upon receiving resource reservation information indicating that the resource reservation application is successful; the VNFM is configured to initiating a resource instantiation request to the VIM according to the resource reservation information; the RO is configured to receive the resource reservation application from the VNFO, only when a resource of the single-domain in which the RO is located is insufficient and a cross-domain resource reservation application is required, transmitting the cross-domain resource reservation application to the CDRO, and when the resource of the single-domain in which the RO is located is sufficient, interacts with the VIM to transmit the resource reservation application in the single-domain in which the RO is located to the VIM.