A major revision on the premonitory demission right has been made by article 17 of Personnel Management Regulations of Public Institutions. The premonitory demission right can be agreed by two sides of the contract, and there is no limit to the “agreement ". The “agreement “is easily out of control without the limit, and is easily unfair to the public institution staff. The balance between the protection of public interests and the protection of the permanent staff’s private rights is the legislative value orientation of the system of the premonitory demission right. The "necessity" of public service maintenance is the reasonable limit of "agreement”. The grasp of the “necessity " should be based on the comprehensive analysis to the core content of the institution staff’s premonitory demission right.