The invention discloses an anti-theft hexagonal socket nut. The anti-theft hexagonal socket nut comprises a first column body, a second column body, a plug, a shielding block, movable rods, a pull wire, springs, side grooves and a limiting rod, wherein the bottom of the first column body is connected with the second column body, and the first column body and the second column body are both cylindrical; the first column body is provided with a regular hexagonal screwing hole with an upper end opening, and the second column body is provided with a threaded hole with an open end opening; the plurality of side grooves are formed in the side wall of the screwing hole, and a through hole is formed in the groove bottom of each side groove and penetrates through the outer wall of the first columnbody; the movable rod is plugged on each through hole, and a limiting disc is arranged on each movable rod; and the spring is clamped between the groove bottom of each side groove and the corresponding limiting disc. According to the anti-theft hexagonal socket nut, the plug, the shielding block and the screwing hole are matched, so that the nut is screwed easily when the plug and the shielding block are not installed and is not screwed easily after the plug and the shielding block are installed, and the good anti-theft effect is achieved.