The invention discloses a frame folding mechanism for a folding bicycle. The frame folding mechanism comprises a connection component which is fixedly connected with a front fork vertical tube, first gears which are relatively fixedly connected to the connection component, second gears which are relatively fixedly connected to cross beams and are meshed with the first gears and a gear lock-up component which is connected onto the cross beams and is used for preventing the first gears and the second gears from relatively rotating, wherein the connection component is rotatably connected with main beams. The frame folding mechanism can be used for folding electric bicycles and folding bicycles, and has the advantages that the bearing capacity is high; the service life is long; slippage does not easily happen; and the safety is high.