The utility model relates to a novel case of a computer mainframe. The novel case comprises a case body, a side cover and a lock and is characterized in that the side cover of the case body can be rotatably opened; a movable part is connected with the case body at one edge of the side cover; the movable part can lead the side cover to rotate along the case body; and the movable part can be the metal rotating page. The lock is arranged at the other edge of the side cover; when a key is inserted into the hole of the lock, the lock is opened, and the side cover can be rotatably opened along the case body, therefore, the strength is saved, the operation is convenient, and a screwdriver is not needed. With the adoption of the lock, the computer accessories in the case can be protected, thereby improving the anti-theft property of the case.