The invention discloses a wet-type high-peel-strength polyurethane resin and a preparation method thereof. According to the invention, a special polyester polyol is adopted; the difference of the special polyester polyol from the common adipic acid series polyester in that the polyester polyol has a soft segment structure, the flexibility of the soft segment part in the molecular chain is reducedand the rigidity is increased due to the rigid chain segment with a benzene ring in the polyester polyol, so that the polyurethane resin has excellent peel strength; the terephthalic acid dihydric diol structure of the polyester is similar to the molecular structure of the polyester cloth, so that the resin can be well combined with a cloth base during tanning; and based on the low flexibility ofthe terephthalic acid chain segment, the crystallization of the soft segment is reduced, so that the phase separation of the soft segment and the hard segment is reduced, the cohesion is reduced, thecurling degree during leather surface drying is reduced, and the leather surface flatness is improved.