Abstract: A medical tissue adhesive and a preparation method thereof. The medical tissue adhesive includes: a functional component, an assistant crosslinker and a dispersing agent. The functional component is a polymer chain modified by tissue adhesive group or a micro nano particle modified by tissue-adhering functional groups. The tissue-adhering functional groups includes: o-nitrobenzyl photoplate group, active ester group or carbonyl group. The medical tissue adhesive not only uses the dispersing agent to expel the tissue fluid/blood on the tissue surface, so that the adhesive molecular segment quickly forms a chemical bond with the amino group on the tissue surface to form a strong tissue adhesive force. But the medical tissue adhesive can also trigger the adhesive molecular segment to react with the amino group on the assistant crosslinker, so that the medical tissue adhesive can quickly gel and solidify. Therefore, it has good bleeding performance, hemostatic performance and tissue adhesion performance.