The invention relates to a hidden locking mechanism, which comprises a mounting sleeve provided with a U-shaped hook. Clamping grooves are formed in the side surfaces of two end feet of the U-shaped hook correspondingly, and stretching-in holes for allowing the end feet of the U-shaped hook to stretch into are formed in the surface of the outer side of the mounting sleeve; a locking plate is arranged in the mounting sleeve, and locking holes corresponding to the end feet one to one and communicating with the stretching-in holes are formed in the locking plate; the locking holes are composed offirst open holes and second open holes which communicate, wherein the first open holes allow the end feet to pass through, and the second open holes are matched with the parts, provided with the clamping grooves, on the end feet; a driving mechanism driving the locking plate to move in the direction from the second open holes to the first open holes is further arranged on the mounting sleeve; andduring assembly, the two end feet of the U-shaped hook are inserted into the stretching-in holes, thus the locking holes correspond to the parts, provided with the clamping grooves, on the end feet,then the driving mechanism drives the locking plate to move in the direction from the second open holes to the first open holes, thus the second open holes are in clamping fit with the clamping grooves, and then the U-shaped hook can be fixed. Disassembling and assembling are both very convenient, and meanwhile the overall appearance is guaranteed.