Chitosan (CS) was proposed as a promising candidate scaffold for tissue engineering. However, some drawbacks of natural CS remain. The current study modified CS by conjugating thiol to CS polymer (Thio-CS) and substantiated its three-dimensional microstructure and physical properties such as swelling or degradation. The Thio-CS was obtained by CS modification using 2-iminothiolane-HCl (2-IT). Because of the formation of disulfide bonds between thiol moieties based on oxidation of the immobilized thiol groups of CS, Thio-CS exhibits in situ gelling properties according to the reducing amount of free thiol. The content of the thiol group was increased as the amount of 2-IT increased. The swelling test demonstrated that Thio-CS can absorb up to 3.5 times its weight of phosphate buffered saline within 1 h and that the pore size and amount significantly increased with incubation time. The Thio-CS enzymatic degradation rate according to velocity was investigated. The results showed that Thio-CS was more resistant to lysozyme as viscosity increased. Thio-CS sponges were fabricated using freeze-drying. The lyophilized Thio-CS had a homogeneous honeycomb-like shape, and its pores were relatively smaller (<2 ${mu}m$) than those of unmodified CS (>2 ${mu}m$). These results suggest that Thio-CS might be a candidate regenerative therapeutic device.