A method and apparatus of security negotiation for handover between different radio access technologies are provided. The method includes: transmitting the security information of the NAS and AS selected by the target system to the UE when the UE hands over between different radio access technologies. Therefore, the UE can perform security negotiation with the target system according to the security information of the NAS and AS. Through the embodiments of the present invention, the UE may obtain the key parameter information of the NAS and AS selected by the LTE system and perform security negotiation with the LTE system when the UE hands over from a different system, such as a UTRAN, to an LTE system.