The present invention provides a method, a device and a system for controlling VoIP border security. The system includes: a border security controller, which includes two dynamic information tables, an active session information table and a registered user information table, acting as the basis of security control; and a security policy server, in communication with the border security controller, adapted to provide a security policy to the border security controller and check the security of a signaling packet forwarded by the border security controller. The border security control system first checks the security and processes the packets of a user datagram received according to the active session information table and the registered user information table, and allows a packet which passed the security processing to pass, and then performs protocol processing on the media packet and signaling packet which are allowed to pass.