The application discloses a method and an apparatus for modifying a network slice instance, and is used for modifying the network slice instance. The method for modifying the network slice instance comprises that: a first network device receives a first request from a second network device, wherein the first request comprises an identifier of the network slice instance, the identifier of a networkslice sub-network instance, and the indication information; the indication information is used for instructing the first network device to add the network slice sub-network instance to the network slice instance, or is used for instructing the first network device to delete the network slice sub-network instance from the network slice instance; and the first network device adds the network slicesub-network instance to the network slice instance according to the first request, or deletes the network slice sub-network instance from the network slice instance according to the first request. Theapplication relates to the technical field of communications.