A synchronization system for detecting asymmetry of optical fibers is provided, which includes a time synchronization correction device, a time delay compensation unit and an optical module device, wherein the optical module device is configured to detect a pulse transmission time delay difference and an asymmetry distance of bidirectional optical fibers between network elements on two sides and to obtain an asymmetry time delay of the bidirectional optical fibers according to the asymmetry distance of the bidirectional optical fibers and the pulse transmission time delay difference. A synchronization method for detecting asymmetry of optical fibers is also provided, which includes obtaining an asymmetry time delay of bidirectional optical fibers according to an asymmetry distance of the bidirectional optical fibers and a pulse transmission time delay difference. A master optical module device and a slave optical module device for detecting asymmetry of optical fibers are also provided.