A network slice management method, a management unit, and a system, where the method includes receiving, by a first management unit, a first management request, where the first management request carries requirement information of a network slice or indication information, and the indication information is used to obtain the requirement information of the network slice. The method further includes determining, by the first management unit, requirement information of a subnet that forms the network slice. According to the method, the first management unit can determine the corresponding requirement information of the subnet based on the requirement information of the network slice.