With the continuous development of modern biomedical field, the performance requirements of injectable and self-healing hydrogel are increasing. Improving adhesion property to meet the practical applications while satisfying injectable and self-healing properties is an urgent problem to be solved. Polysaccharide based GA-CS/OKGM hydrogel with injectable, self-healing, and adhesion properties was successfully prepared by modifying chitosan (CS) with gallic acid (GA) and then dynamically crosslinked with oxidized konjac glucomannan (OKGM). The synergistic effect of dynamic imine bonding, hydrogen bonding, and electrostatic interactions in polymer network endows the hydrogel with injectable, self-healing, and shape-adaptability properties. This is structural similiarity between the polyphenol moiety in gallic acid and mussel catechol moiety, endowing adhesive property to the hydrogel. In addition, GA-CS/OKGM hydrogel has excellent biocompatibility, biodegradability, and good mechanical properties, which is a promising smart biomaterial in biomedical fields.