|According to the Charter of the United Nations and its staff regulation, the Sectary-General has the discretionary power to decide the merits and ability of the staff of the Secretariat. This kind of regulations is reasonable if the specialty and technicality of the staff of the United Nations is taken into consideration. However, if too much discretionary power has been authorized to the Sectary-General, the power could be abused. Therefore, in order to protect the rights of the staff, it is important to have an institution to limit the power of the Sectary-General. The United Nations Administrative Tribunal, established in 1949, is the only organ which could balance the discretionary power of the Sectary-General. This article hopes, through analyzing the cases of United Nations Administrative Tribunal, to understand how the Tribunal reviews the administrative acts based on the discretion. This article categorizes the Tribunal's review into four parts: (1) the review of facts; (2) the review of motive; (3) the review of contents; (4) the review of procedure.