Abstract: The reactive oxygen species (ROS), like hydrogen peroxide (H₂O₂), generated commonly during metabolism, and the increased level of H₂O₂ in tumor cells could be up to 0.5 nmol/(10⁴ cells·h) in comparison with that in normal cells, which provided a possibility for the usage of oxidation-responsive hydrogels in biomedical field. Herein, di-(1-hydroxylundecyl) diselenide was prepared by the nucleophilic substitution reaction between sodium diselenide (Na₂Se₂) and 11-bromoundecanol, and then reacted with isophorone diisocyanate (IPDI) into an isocyanate-terminated diselenide crosslinker. Finally, a diselenide dextran hydrogel was synthesized by crosslinking dextran with the diselenide agent. The structure, swelling profile, oxidation-responsive capability, rheology property, and in vitro drug release behavior of the diselenide dextran hydrogel were characterized by proton nuclear magnetic resonance (¹H-NMR) spectrum, Fourier-transform infrared (FT-IR) spectra, gel permeation chromatography (GPC), Raman spectrum, rotational rheometer, and ultraviolet-visible (UV-Vis) spectrophotometry. Results demonstrated that the hydrogel with a lower crosslinking degree showed a higher swelling ratio. In addition, the dissolution of hydrogel was observed visually after adding H₂O₂ solution due to the decomposition of diselenide bonds in the polymer network, indicating that the resultant hydrogel could be in response to the oxidation stimulus. Furthermore, in vitro drug release experiments were carried out by using rhodamin B (RhB) as a model agent. The results revealed that the hydrogel could only release 45% of the loaded drug in 24 h without H₂O₂, while 90% of the loaded drug could be released in 14 h under an oxidizing environment (i.e., w(H₂O₂)=0.2%), indicating that the diselenide dextran hydrogel was a promising candidate for drug release.