A spinal interbody cage, comprising: an upper plate having a plurality of upper plate slanted surfaces; a lower plate having a plurality of lower plate slanted surfaces; a screw arbor disposed between the upper plate and the lower plate and having a first section and a second section, the sections having an outer thread respectively, wherein the outer thread of the first section and outer thread of the second section are of opposite spiral direction; and a first slide block and a second slide block, wherein the slide blocks are disposed between the upper plate and the lower plate and have a through hole (311, 321) having an inner thread respectively, and the inner threads are of opposite spiral direction, wherein the outer threads of the screw arbor are disposed in and cooperate with the inner threads of the first slide block and the second slide block, and the screw arbor, the first slide block and the second slide block are disposed between the upper plate and the lower plate, and the upper plate slanted surfaces face the lower plate respectively, the lower plate slanted surfaces face the upper plate respectively, the first slide block and the second slide block include at least two slide block slanted surfaces respectively, and the slide block slanted surfaces abut against one of the upper plate slanted surfaces and the lower plate slanted surfaces respectively, wherein the upper plate slanted surfaces, the lower plate slanted surfaces and the slide block slanted surfaces are configured so that when the screw arbor is rotating in the direction of the long axis X, the first slide block will be driven to distance itself from the second slide block and cause the upper plate to distance itself from the lower plate along the vertical direction, wherein the upper plate has a pair of upper plate protruding portions protruding toward the lower plate, the upper plate protruding portions are laterally opposite and have an upper plate constraint member respectively, the lower plate has a pair of lower plate protruding portions protruding toward the upper plate, the lower plate protruding portions are laterally opposite and have a lower plate constraint member respectively, wherein the upper plate constraint members and the lower plate constraint members are configured to define a maximum value of the variable height of the spinal interbody cage. an upper plate having a plurality of upper plate slanted surfaces; a lower plate having a plurality of lower plate slanted surfaces; a screw arbor disposed between the upper plate and the lower plate and having a first section and a second section, the sections having an outer thread respectively, wherein the outer thread of the first section and outer thread of the second section are of opposite spiral direction; and a first slide block and a second slide block, wherein the slide blocks are disposed between the upper plate and the lower plate and have a through hole (311, 321) having an inner thread respectively, and the inner threads are of opposite spiral direction, wherein the outer threads of the screw arbor are disposed in and cooperate with the inner threads of the first slide block and the second slide block, and the screw arbor, the first slide block and the second slide block are disposed between the upper plate and the lower plate, and the upper plate slanted surfaces face the lower plate respectively, the lower plate slanted surfaces face the upper plate respectively, the first slide block and the second slide block include at least two slide block slanted surfaces respectively, and the slide block slanted surfaces abut against one of the upper plate slanted surfaces and the lower plate slanted surfaces respectively, wherein the upper plate slanted surfaces, the lower plate slanted surfaces and the slide block slanted surfaces are configured so that when the screw arbor is rotating in the direction of the long axis X, the first slide block will be driven to distance itself from the second slide block and cause the upper plate to distance itself from the lower plate along the vertical direction, wherein the upper plate has a pair of upper plate protruding portions protruding toward the lower plate, the upper plate protruding portions are laterally opposite and have an upper plate constraint member respectively, the lower plate has a pair of lower plate protruding portions protruding toward the upper plate, the lower plate protruding portions are laterally opposite and have a lower plate constraint member respectively, wherein the upper plate constraint members and the lower plate constraint members are configured to define a maximum value of the variable height of the spinal interbody cage.