A network slice deployment method, comprising: obtaining, by a network slice deployment apparatus, slice coexistence relationship information of a first network slice, wherein the slice coexistence relationship information is used to indicate information about a second network slice that has a slice coexistence relationship with the first network slice; determining, by the network slice deployment apparatus, based on the slice coexistence relationship information, a deployment mode of a network function entity required by the first network slice; and deploying, by the network slice deployment apparatus, the network function entity in the deployment mode; wherein the network function entity required by the first network slice is a mobility management network element; wherein the slice coexistence relationship information comprises a coexistence network slice type list, and the coexistence network slice type list comprises a slice type of the second network slice; characterized in that the determining, based on the slice coexistence relationship information, a deployment mode of a network function entity required by the first network slice comprises: determining whether a network slice instance corresponding to the slice type of the second network slice exists; and when the network slice instance corresponding to the slice type of the second network slice exists, determining that the deployment mode of the mobility management network element required by the first network slice is a sharing mode; and when the network slice instance corresponding to the slice type of the second network slice does not exist, determining that the deployment mode of the mobility management network element required by the first network slice is a creation mode. obtaining, by a network slice deployment apparatus, slice coexistence relationship information of a first network slice, wherein the slice coexistence relationship information is used to indicate information about a second network slice that has a slice coexistence relationship with the first network slice; determining, by the network slice deployment apparatus, based on the slice coexistence relationship information, a deployment mode of a network function entity required by the first network slice; and deploying, by the network slice deployment apparatus, the network function entity in the deployment mode; wherein the network function entity required by the first network slice is a mobility management network element; wherein the slice coexistence relationship information comprises a coexistence network slice type list, and the coexistence network slice type list comprises a slice type of the second network slice; characterized in that the determining, based on the slice coexistence relationship information, a deployment mode of a network function entity required by the first network slice comprises: determining whether a network slice instance corresponding to the slice type of the second network slice exists; and when the network slice instance corresponding to the slice type of the second network slice exists, determining that the deployment mode of the mobility management network element required by the first network slice is a sharing mode; and when the network slice instance corresponding to the slice type of the second network slice does not exist, determining that the deployment mode of the mobility management network element required by the first network slice is a creation mode. determining whether a network slice instance corresponding to the slice type of the second network slice exists; and when the network slice instance corresponding to the slice type of the second network slice exists, determining that the deployment mode of the mobility management network element required by the first network slice is a sharing mode; and when the network slice instance corresponding to the slice type of the second network slice does not exist, determining that the deployment mode of the mobility management network element required by the first network slice is a creation mode.