The invention relates to a polyurethane hot-melt adhesive for bonding and a preparation method thereof, belonging to the technical field of preparation of automobile hot-melt adhesives. The preparation method comprises the following steps of: firstly, feeding high-crystalline polyester glycol, polyester polyol and tackifying resin into a reactor, heating, dehydrating at vacuum while stirring, andthen cooling; secondly, preheating diisocyanate, adding the preheated diisocyanate to the reactor to uniformly stir and carrying out prepolymerization reaction; after the prepolymerization is finished, sequentially adding weighed catalyst, antioxidant, coupling agent, viscosity stabilizer and grey paste under nitrogen circulation, and stirring till being mixed uniformly; discharging in the nitrogen protection condition, sealing and packaging so as to obtain the product, that is, the polyurethane hot-melt adhesive for bonding automobile lights. The hot-melt adhesive prepared by adopting the preparation method disclosed by the invention can be used for bonding a plurality of base materials such as PP (Polypropylene), PBT (polybutylece terephthalate), ABS (Acrylonitrile Butadiene Styrene), PMMA (polymethyl methacrylate), PC (Poly Carbonate) and inorganic glass.