The present invention relates to a liquid composition including alginic acid or a pharmaceutically acceptable salt thereof and a colloidal polysaccharide. The liquid composition of the present invention is suitable as a medical biomaterial for tissue repair to elevate mucosal tissues of the stomach and intestines during endoscopic resection. More specifically, the present invention relates to a submucosal injectable pharmaceutical liquid composition for use in endoscopic mucosal resection (EMR) or endoscopic submucosal dissection (ESD) for medical applications, including alginic acid having a weight average molecular weight of 100,000 to less than 200,000 or a pharmaceutically acceptable salt thereof and a colloidal polysaccharide. The liquid composition of the present invention is suitable for use as a preparation for submucosal local injection that can maintain mucosal elevation for a long time when injected during endoscopic mucosal resection or endoscopic submucosal dissection.
