Endoscopic submucosal dissection (ESD) is widely used to treat gastrointestinal mucosal and submucosal lesions. However, it may cause bleeding, perforation, and stricture. Although these complications can be avoided by introducing materials such as polyglycolic acid and carboxymethyl cellulose sheets, such approaches are expensive and time-consuming. Herein, we report a hydrogel prepared by combining a colloidal solution composed of konjac glucomannan (KGM) and sodium alginate (SA) and a fixative solution containing ε-poly-l-lysine (ε-PLL) and calcium chloride. The two solutions were mixed on the wound surface to form the KGM/SA/ε-PLL hydrogel through hydrogen bonds, coordination bonds, and electrostatic attraction. The effectiveness and convenience of applying the KGM/SA/ε-PLL hydrogel to promote wound healing in the esophagus and colon were assessed in vitro and in vivo. We found that the hydrogel stimulated epithelial proliferation, reduced inflammation, promoted recapillarization, and inhibited fibrosis in the esophagus and colon. Therefore, the KGM/SA/ε-PLL hydrogel is an effective and convenient agent that can promote post-ESD wound healing and is recommended for ulcer bed protection in daily clinical practice.