The utility model discloses a bottle cap locking device of a bottle, aiming at providing a bottle bottle cap locking device, which is characterized in that the bottle cap is locked tightly and the open side of the bottle cap can be directly opposite to the bottle body propaganda mark after screwing. The technical scheme adopted by the utility model is that: the bottle body is screwed to the bottle cap at the outlet end through a mutually cooperating screw thread, and the joints between the bottle body and the bottle cap have mutually cooperating bosses and clamping positions to lock the bottle cap. The said card position is located between the two wedges on the bottom of the screw thread and the two wedges are opposite to each other, and the two wedges are opposite to each other and form a right angle convex, and gradually smooth outward until they merge with the bottom of the thread surface. The said boss is located in the bottle. The combined end face of the cover and the outlet end is matched with the shape and position of the cover, and the boss on the bottle cover is set in an appropriate position so that the opening side of the bottle cover can be directly opposite to the product propaganda mark on the bottle body; The new type can be widely applied to the design of cosmetics or other product bottles.