A transmission system includes two or more independent chambers, in each of which shafts with gears thereon are provided for rolling in synchronous motion, and a carrier with adjustable gear devices on a bottom thereof. Each of the adjustable gear devices has a base, a movable rack member, vertical springs and horizontal springs. The movable rack member is connected to the base to be moved along a horizontal direction. The vertical springs are provided between the base and the carrier to urge the adjustable gear device along a vertical direction. The movable rack member has a rack portion to be meshed with the gears of the shafts, such that the carrier is moved by the gears to cross the chambers. With the movement of the movable rack member both along the horizontal and the vertical direction, the carrier is transported in a smooth, synchronous, skid-proof, stable and real-time motion during the crossing chamber process.