A hydrogel, characterized in that , the hydrogel is prepared by gelation of a system comprising a sulfhydryl-modified polymer compound, wherein the sulfhydryl-modified polymer compound is at least one of the following series of compounds: a series of sulfhydryl-modified polymer compounds, wherein to-be-modified polymer compounds comprise at least one selected from -COOH, -NH 2 , -OH, an acrylate group of formula a, an acrylamide group of formula b and an acryloyl group of formula c in the structure, wherein part or all of the -COOH and/or the -NH 2 and/or the -OH and/or the acrylate group and/or the acrylamide group and/or the acryloyl group are modified to form a side chain with the following terminal group: wherein in the above group, * represents a linking site; R 1 is selected from hydrogen, halogen, an aliphatic group, an aromatic group and the like; R 2 and R 3 are the same or different and independently from each other, and are selected from hydrogen, halogen, an aliphatic group, an aromatic group and the like; R 4 is a polysulfhydryl compound fragment; the system further comprises at least one of the following substances: C1. an acryloylated polymer compound, and C2. a small molecule cross-linking agent containing an acryloyl group; wherein the substance C2, the small molecule cross-linking agent containing an acryloyl group, includes at least one of the following substanes: ethylene glycol diacrylate (EGDA), polyethylene glycol diacrylate (PEGDA), trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate (PTA), pentaerythritol tetraacrylate (PTTA), di(trimethylolpropane) tetraacrylate (DTTA). a series of sulfhydryl-modified polymer compounds, wherein to-be-modified polymer compounds comprise at least one selected from -COOH, -NH 2 , -OH, an acrylate group of formula a, an acrylamide group of formula b and an acryloyl group of formula c in the structure, wherein part or all of the -COOH and/or the -NH 2 and/or the -OH and/or the acrylate group and/or the acrylamide group and/or the acryloyl group are modified to form a side chain with the following terminal group: wherein in the above group, * represents a linking site; R 1 is selected from hydrogen, halogen, an aliphatic group, an aromatic group and the like; R 2 and R 3 are the same or different and independently from each other, and are selected from hydrogen, halogen, an aliphatic group, an aromatic group and the like; R 4 is a polysulfhydryl compound fragment; the system further comprises at least one of the following substances: C1. an acryloylated polymer compound, and C2. a small molecule cross-linking agent containing an acryloyl group; wherein the substance C2, the small molecule cross-linking agent containing an acryloyl group, includes at least one of the following substanes: ethylene glycol diacrylate (EGDA), polyethylene glycol diacrylate (PEGDA), trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate (PTA), pentaerythritol tetraacrylate (PTTA), di(trimethylolpropane) tetraacrylate (DTTA). C1. an acryloylated polymer compound, and C2. a small molecule cross-linking agent containing an acryloyl group; wherein the substance C2, the small molecule cross-linking agent containing an acryloyl group, includes at least one of the following substanes: ethylene glycol diacrylate (EGDA), polyethylene glycol diacrylate (PEGDA), trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate (PTA), pentaerythritol tetraacrylate (PTTA), di(trimethylolpropane) tetraacrylate (DTTA). <EOS>