Substrates with basic structures similar to those of living tissues are useful as cellular scaffolds for the preparation of biocompatible and innocuous materials. In this study, a hydrogel matrix was prepared by introducing a functional group capable of forming crosslinks between natural polymers to create a basis for preparing a microenvironment favorable for cell adaptation. The modified dextran hydrogel polymer was designed to mimic the conditions of the extracellular matrix (ECM) as a scaffold. The precursors of the target hydrogel were synthesized using condensation with a stepwise procedure. A delicate hydrogel based on modified dextran was obtained via photo-crosslinking under room temperature at UV-254 nm. The biocompatibility of this hydrogel was verified using green fluorescence images acquired by incubating a cell line. The characteristics of the hydrogel were verified using proton nuclear magnetic resonance (1H NMR), Fourier-transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD) analysis, and electrostatic spinning. The crosslinked structure and biocompatibility of the modified hydrogel were confirmed using instrumental analyses and a promising cell culture. Using TGA, the weight losses of precursor and hydrogel were determined to be 90.96% and 39.2%, respectively, up to 600 °C. The diameters of the nanofibers, fabricated via electrospinning, were measured to range from 200 to 500 nm.