The invention discloses a network slice modification method and device, which is used for solving the problem that the existing NSI modifying mode cannot meet the end-to-end service requirement. The method comprises the following steps that the first NSSMF receives a first management message sent by the NSSMF, wherein the first management message is used for requesting the first NSSMF to modify the first NSSI to be modified, the first management message carries modification demand information for modifying the first NSSI, and the first NSSMF is an NSSMF for managing the first NSSI; the first NSSMF completes modification for the first NSI based on the modification demand information of the first NSI; and when the first NSSMF determines that the TN part of the transmission network related tothe first NSSI needs to be modified, the first NSSMF sends a second management message to a transmission network management system for managing the TN, and the second management message carries modification demand information for modifying the TN part.