Abstract: The present invention provides an alginic acid-based injectable hydrogel system for labeling an accurate position of a disease lesion and effectively delivering a drug to a target region. The formulation of the present invention can make it easy to locally inject a contrast agent and a drug into a target region while controlling the release rate of the contrast agent or the drug, with the formation of the hydrogel in the injected region. Through the advantages, the labeled position can be accurately determined from images, thereby enhancing the precision of surgical operation, with a minimal incision formed therefor. In addition, when used, the alginic acid-based injectable hydrogel system allows the effective local delivery of a drug to a target region while increasing the long-acting effect of the drug.