The invention discloses a preparation method and application of a hyperbranched polyester based polyurethane medical adhesive. The preparation method comprises the following steps: 1) taking hydroxyl-terminated hyperbranched polyester and acryloyl chloride to react, and obtaining a series of double-bond modified precursors 1 through a regulation and control ratio, wherein the mol ratio of -OH in the hydroxyl-terminated hyperbranched polyester to the acryloyl chloride is 1 to (2 to 4); 2) feeding diisocyanate and polyethylene glycol according to the mol ratio of 2 to 1 and reacting to obtain aprecursor 2; 3) taking the precursor 1 and the precursor 2 to react according to the ratio of a -OH functional group number of the precursor 1 to a -NCO functional group number of the precursor 2 of 1to (1.1 to 2.0), so as to obtain a double-bond-containing hyperbranched polyester based polyurethane medical adhesive; 4) uniformly mixing the hyperbranched polyester based polyurethane medical adhesive with 0.1 to 0.5 weight percent of photoinitiator i2595 and preserving in a dark place for later use. The medical adhesive prepared by the preparation method has no toxicity and harms, good biocompatibility and a strong chemical adhesive force on human tissues.