A method for managing a network slice instance, comprising: receiving, by a first network device, an update request message sent by a transmit end, wherein the update request message carries identification information of a first network slice instance, and the update request message is used to request to update a first network function of the first network slice instance to a second network function; sending, by the first network device, a first configuration request message to a second network device based on the update request message, wherein the first configuration request message is used to request to configure the second network function for the first network slice instance; receiving, by the first network device, a configuration response message sent by the second network device based on the first configuration request message, wherein the configuration response message is used to indicate that the second network function has been configured; and sending, by the first network device, an update response message to the transmit end based on the configuration response message, wherein the update response message is used to indicate that the first network function has been updated to the second network function; wherein before the sending, by the first network device, a first configuration request message to a second network device based on the update request message, the method further comprises: sending, by the first network device, a creation request message to a third network device when no available second network function exists and the second network function is a virtualized network function, wherein the creation request message is used to request to create the second network function, and the creation request message carries a parameter of the second network function; and receiving, by the first network device, a first response message sent by the third network device based on the creation request message, wherein the first response message is used to indicate that the second network function has been created; and the sending, by the first network device, a first configuration request message to a second network device based on the update request message comprises: sending, by the first network device, the first configuration request message to the second network device based on the first response message. receiving, by a first network device, an update request message sent by a transmit end, wherein the update request message carries identification information of a first network slice instance, and the update request message is used to request to update a first network function of the first network slice instance to a second network function; sending, by the first network device, a first configuration request message to a second network device based on the update request message, wherein the first configuration request message is used to request to configure the second network function for the first network slice instance; receiving, by the first network device, a configuration response message sent by the second network device based on the first configuration request message, wherein the configuration response message is used to indicate that the second network function has been configured; and sending, by the first network device, an update response message to the transmit end based on the configuration response message, wherein the update response message is used to indicate that the first network function has been updated to the second network function; wherein before the sending, by the first network device, a first configuration request message to a second network device based on the update request message, the method further comprises: sending, by the first network device, a creation request message to a third network device when no available second network function exists and the second network function is a virtualized network function, wherein the creation request message is used to request to create the second network function, and the creation request message carries a parameter of the second network function; and receiving, by the first network device, a first response message sent by the third network device based on the creation request message, wherein the first response message is used to indicate that the second network function has been created; and the sending, by the first network device, a first configuration request message to a second network device based on the update request message comprises: sending, by the first network device, the first configuration request message to the second network device based on the first response message. sending, by the first network device, a creation request message to a third network device when no available second network function exists and the second network function is a virtualized network function, wherein the creation request message is used to request to create the second network function, and the creation request message carries a parameter of the second network function; and receiving, by the first network device, a first response message sent by the third network device based on the creation request message, wherein the first response message is used to indicate that the second network function has been created; and the sending, by the first network device, a first configuration request message to a second network device based on the update request message comprises: sending, by the first network device, the first configuration request message to the second network device based on the first response message.