The invention provides a height-adjustable fusion cage, which comprises a fusion cage base, a transmission block, a retaining ring, an upper cover plate and a lower cover plate, wherein the transmission block is arranged in the fusion cage base, and the specific position of the transmission block is adjusted via a screw, so that the transmission block can do axial movement in the fusion cage base;along with the movement of the transmission block, the upper cover plate and the lower cover plate, which are connected to the transmission block in a clamped and embedded mode, do synchronous movement along the direction of convex ribs of the transmission block convex ribs, so that a distance between the upper cover plate and the lower cover plate is changed, and the height of the fusion cage isadjusted. According to the height-adjustable fusion cage provided by the invention, the position of the transmission block is adjusted via the screw, and the height of the fusion cage is adjusted through a linkage action between the transmission block and the upper and lower cover plates, which move in the front-back direction, so that continuous adjustment of the fusion cage in accordance with models and sizes is achieved and various individual demands are satisfied. Meanwhile, the height-adjustable fusion cage has the advantages of being small in size, convenient to implant, applicable to minimally invasive spinal fusion under an endoscope, beneficial for promoting minimal invasion of interbody fusion and the like.