The invention provides an expanding blade, comprising a first snap-fit portion, a second snap-fit portion, a fixation portion, a partition panel and hook edges, wherein, the first snap-fit portion has an axial flat section on one side； the second snap-fit portion is connected with the first snap-fit portion at one end and fixed to the fixation portion at the other end, and a convex locating block is arranged on the side wall of the second snap-fit portion； the partition panel is connected with the fixation portion at one end, the hook edges which are inclined outwards is arranged at the other end, and both the fixation portion and the hook edges are arranged on the same side of the partition panel. In addition, the invention also puts forward a unidirectional expanding device and a bidirectional expanding device which use the expanding blade. In this application, two fastening structures, i.e. the first snap-fit portion and the second snap-fit portion, arranged for the expanding blade can be snap-fitted in with different devices using different installation methods. Both the unidirectional expanding device and the bidirectional expanding device can also use the same kind of expanding blades, which reduces the number of instruments used in operations and lowers the cost, and both of them are simply fastened with simple structures, which is convenient for disassembly, assembly and replacement.
