A method for negotiating security capabilities during movement of a User Equipment (UE) includes the following steps: a target network entity receives a Routing Area Update (RAU) Request from the UE; the entity obtains Authentication Vector (AV)-related keys deduced according to a root key, and sends the selected security algorithm to the UE; and the UE deduces the AV-related keys according to the root key of the UE. A system, SGSN, and MME for negotiating security capabilities during movement of a UE are also disclosed. The present invention is applicable to security capability negotiation between the UE and the network.