A self-opening cigarette case includes an external case with an aperture on the top and a core box. A hole is available at the bottom case of the external case. The core box is movable and can be inserted into the external case from the top aperture of the external case. An aperture is opened on the top of the core box, where a rotational cover is equipped. The bottom of the case is connected, through a connecting shaft, to the top edge of the side wall on the back of the core box. A torsion spring is provided on the connecting shaft, one end of which supports the cover, and the other end supports the side wall on the back of the core box. A groove skipping is equipped on every external side of the two side walls on the left and right of the core box. Proportionally, a lobe is equipped on the internal sides of left and right walls of the external case in order to match with the groove skipping. The advantages of the case lie in that it is convenient and reliable for use since the core box is entirely closed and the cover can turn over automatically. The cigarettes will not fall off due to carelessness. A protective structure is equipped with the prevention of the separation of the external case and the core box, the core box will not be pushed out of the external case, due to a forcibly push, causing the core box and the cigarettes within it to scatter to the ground.