The invention relates to a kind of polyethylene glycol amino acid N-inner ring carbonyl-anhydride activity derivative with I as general formula. In the general formula, n and m are integers among 1-6; j is integer among 1-20; X is linking group; Y is a hydroxyl of PFG or a stop-end by C1-12 alkoxyl, cycloalkoyl, or aralkoxyl. The invention also offers the derivative of general formula I and the matter containing free amino group, such as a linkage matter formed with albumen, polypeptide, synthetic polymer, and therapeutic agent, and the linkage matter has improved bioavailability, physiological half-life, and water solubility. The invention still offers a gel produced by polymerization with the activity derivative itself or with other polymer or copolymerization with other minor molecule amino acid compound, and also offers its manufacturing method of this derivative and medicine usefulness of the gel.