A method applied to processing of access stratum (AS) security for terminal handover from a source cell to a target cell, including obtaining a derivation parameter, deriving a target AS root key based on a source AS root key and derivation parameter, and calculating, based on the target AS root key, an AS security key used in the target cell. The source AS root key is an AS root key used in the source cell, the target AS root key is an AS root key used in the target cell, the derivation parameter is used to derive an AS root key and corresponds to a RAN node or a RAN node group or an area in which the target cell is located, and cells at a same RAN node, RAN node group, or area have a same derivation parameter.