The invention provides a preparation method of star-shaped nano-glue for underwater repair. The preparation method comprises following steps: a), eugenol and triethyl silicane are subjected to first reaction under the action of a first catalyst, and silyl etherified eugenol is obtained; b), silyl etherified eugenol and metachloroperbenzoic acid are subjected to second reaction in a solvent, and epoxy resin silyl eugenol is obtained; c), epoxy resin silyl eugenol, acrylic acid and hydroquinone are subjected to third reaction under the action of a second catalyst, and modified eugenol is obtained; d), modified eugenol, lysine compounds and modified beta-cyclodextrin are subjected to fourth reaction under the action of a third catalyst, protecting groups are removed, and the star-shaped nano-glue is obtained. The star-shaped nano-glue can be cured in water directly, has stronger adsorption capacity, seawater immersion resistance and impact resistance, and is good in biocompatibility and suitable for the underwater repair in the marine environment.