The invention belongs to the field of tissue engineering and discloses chemically-crosslinked natural polysaccharide-based injectable hydrogel, a preparation method thereof and application thereof in tissue engineering materials, especially in conjunctival repair. The preparation method includes the following steps: adding an acrylated natural polysaccharide material water solution into a sulfhydrylated natural polysaccharide material water solution, mixing well, adding a beta-sodium glycerophosphate solution to adjust pH to be neutral, and incubating at temperature of 37 DEG C to obtain the chemically-crosslinked natural polysaccharide-based injectable hydrogel. The hydrogel is controllable in performance, can realize gelation under human physiological conditions, is needless of adding other chemical crosslinking agents, can be used as a tissue engineering material and is especially suitable for conjunctival repair, injectable, quick in reaction, capable of realizing gelation within 5-15min, in-situ in forming, high in surgical operability and automatic in bonding in the process of surgery, stitching for fixing is not needed, and wound surfaces in any shape and at any position can be protected effectively.