The invention provides a nano-material modified solvent-free polyurethane wood paint and a preparation method. The paint comprises, by weight, MDI, polyether polyol, polyester polyol and a prefabricated additive, wherein the prefabricated additive comprises phosphoric acid, a silane coupling agent, neopentyl glycol, polybutylene, nano white carbon black and nano titanium dioxide. The preparation method specifically includes the steps that after a checked reaction kettle is heated, liquid MDI is added and stirred under a nitrogen atmosphere, polyether polyol is added, and the materials continueto be stirred to obtain a polyurethane prepolymer; part of polyester polyol is added and stirred, then the prefabricated additive is added, vacuumizing is conducted to the absolute pressure of 20 mbar, and heating and stirring are conducted; finally, the remaining polyester polyol is added, the materials continue to be stirred under the vacuum state, the product is discharged, and the nano-material modified solvent-free polyurethane wood paint is obtained. The nano-material modified solvent-free polyurethane wood paint prepared through the method serves as a polyurethane framework structure and a crystalline structure, and ageing resistance, hydrolysis resistance and abrasion resistance of the wood paint can be comprehensively improved.