A method for isolation in the CN domain of a network slice includes receiving a slice isolation policy and establishing a CN NSS isolation policy based on the slice isolation policy. When the CN NSS isolation policy includes a network resource isolation policy, the network resource isolation policy is mapped to a network resource allocation policy, a part of which relating to physical resources is sent to a network function management function (NFMF) and a part relating to virtual resources is sent to a network function virtualization management and orchestration function. When the NSS isolation policy includes an application level isolation policy, the application level isolation policy is mapped to an application level policy which is sent to the NFMF.