The invention discloses a boundary violation alarm server, a monitored terminal, a monitoring terminal, a system and a method, and relates to the technical field of computer and communication. The boundary violation alarm server comprises a monitored unit, which is used to monitor the position information reported by a monitored terminal and send the position information to a processing unit; a monitoring unit, which is used to monitor area setting information reported by a monitoring terminal and send the area setting information to the processing unit; and a processing unit, which is used to judge the monitored terminal is in the area where the monitored terminal is allow to move, according to the movement area, which is defined by the area setting information, of the monitored terminal and the position information, and if the monitored terminal exceeds the movement area, the monitoring terminal sends alarm information. The provided boundary violation alarm server, monitored terminal, monitoring terminal, system and method improve the monitoring performance of monitoring user on monitored user.