Foundation bolt length control device

The utility model relates to a length control device for a foundation bolt. The length control device comprises a vertical part and an extension rod of the foundation bolt, the vertical part and the extension rod are each provided with a smooth section and a peripheral threaded section. The thread directions of the vertical part and the peripheral thread section of the extension rod are opposite, and the vertical part and the extension rod are connected through a high-strength nut; the end face, facing the extension rod, of the high-strength nut is provided with a cavity I in the length direction of the high-strength nut. The smooth section of the extension rod is rotatably connected with a turntable I, the turntable I is fixedly connected with a vertical rod I, and the free end of the vertical rod I extends into the cavity I; the width of the cavity I is greater than that of the vertical rod I; a plurality of limiting grooves I are formed in the periphery of the free end of the vertical rod I at intervals in