The present invention relates to a polyethylene glycol hydrogel injection, and, more particularly, to an injection to be administered into a joint (a synovial joint cavity) for the improvement of symptoms of arthritis by containing two separate buffer solutions, wherein a solution (1) contains a polyethylene glycol derivative with an electrophilic functional group and a buffer of pH 3.5 to 6, and a solution (2) contains a polyethylene glycol derivative with a nucleophilic functional group, hyaluronic acid, and a buffer of pH 7.5 to 11. The injection of the present invention is highly biocompatible and long-lasting in the joint, showing the efficacy of pain relief, cartilage protection, and inhibition of inflammation, thus offering the effective prevention and treatment of arthritis.
