A network slice selection method, comprising: obtaining, by a first management unit having a communication service management function, CSMF, a service request message, wherein the service request message is used to initiate a service request for a service of a tenant; and sending, by the first management unit, a network slice request message to a second management unit having a network slicing management function, NSMF, based on the service request message, wherein the network slice request message carries first priority information, the first priority information is used to indicate a priority of the tenant or a priority of the service, and the first priority information is used by the second management unit to select a network slice for the service of the tenant, wherein the method further comprises: determining, by the first management unit, the first priority information based on the service request message, characterized in that the determining, by the first management unit, the first priority information based on the service request message comprises: determining, by the first management unit, a network requirement of the service based on service requirement information of the service, and determining, by the first management unit, the first priority information based on the network requirement of the service, wherein the service requirement information comprises at least one of the following information: a service type, a security level, an isolation level, a throughput, coverage, and a quality of service requirement, and network requirement information comprises at least one of the following information: a latency requirement, a bandwidth requirement, and a network quality of service requirement. obtaining, by a first management unit having a communication service management function, CSMF, a service request message, wherein the service request message is used to initiate a service request for a service of a tenant; and sending, by the first management unit, a network slice request message to a second management unit having a network slicing management function, NSMF, based on the service request message, wherein the network slice request message carries first priority information, the first priority information is used to indicate a priority of the tenant or a priority of the service, and the first priority information is used by the second management unit to select a network slice for the service of the tenant, wherein the method further comprises: determining, by the first management unit, the first priority information based on the service request message, characterized in that the determining, by the first management unit, the first priority information based on the service request message comprises: determining, by the first management unit, a network requirement of the service based on service requirement information of the service, and determining, by the first management unit, the first priority information based on the network requirement of the service, wherein the service requirement information comprises at least one of the following information: a service type, a security level, an isolation level, a throughput, coverage, and a quality of service requirement, and network requirement information comprises at least one of the following information: a latency requirement, a bandwidth requirement, and a network quality of service requirement. determining, by the first management unit, the first priority information based on the service request message, characterized in that the determining, by the first management unit, the first priority information based on the service request message comprises: determining, by the first management unit, a network requirement of the service based on service requirement information of the service, and determining, by the first management unit, the first priority information based on the network requirement of the service, wherein the service requirement information comprises at least one of the following information: a service type, a security level, an isolation level, a throughput, coverage, and a quality of service requirement, and network requirement information comprises at least one of the following information: a latency requirement, a bandwidth requirement, and a network quality of service requirement. determining, by the first management unit, a network requirement of the service based on service requirement information of the service, and determining, by the first management unit, the first priority information based on the network requirement of the service, wherein the service requirement information comprises at least one of the following information: a service type, a security level, an isolation level, a throughput, coverage, and a quality of service requirement, and network requirement information comprises at least one of the following information: a latency requirement, a bandwidth requirement, and a network quality of service requirement.