The invention relates to the technical field of building hardware, and particularly discloses a bidirectional transmission lock box for flat-opened doors and windows. The bidirectional transmission lock box for the flat-opened doors and the windows comprises a first wheel guard plate and a second wheel guard plate, and is characterized in that center holes, threaded column mounting holes, semicircle grooves, ratchet wheel grooves and small windows are formed in the first wheel guard plate and the second wheel guard plate correspondingly, a small mounting hole corresponding to the center hole is formed in the second wheel guard plate, driving gears are mounted in the center holes, a small gear is arranged in the small mounting hole, and clamping columns are arranged in the semicircle grooves; and the driving gears mesh with a first rack and the small gear, and the small gear meshes with a second rack. According to the bidirectional transmission lock box for the flat-opened doors and thewindows, the structure is reasonable, safety and reliability are achieved, the mechanical performance is stable, the transmission accuracy is high, the defects of unattractive mounting, poor transmission performance, poor use experience of the whole windows and the like in the prior art are overcome, the advantage of quick mounting is achieved, and the user experience of the doors and windows isimproved more advantageously.