The present invention relates to a method for preparing a wood modifier and a method for wood modification, and in particular, to a method for preparing a room temperature cured multifunctional wood modifier and a method for wood modification to solve the problems of high construction temperature, high toxicity, poor leaching-resistance and single function of existing wood modifiers. The method includes: step 1: weighing a hydrophobic polymer resin, an additive, a curing agent and a solvent, mixing and then stirring at room temperature to obtain a functional reagent A; step 2: weighing nanoparticles, a surface modifier and toluene, mixing and then stirring, cleaning with acetone, centrifuging, and drying to obtain a functional reagent B; step 3: adding a functional reagent C into the functional reagent A, evenly stirring, adding the functional reagent B, and performing ultrasonic processing to obtain the multifunctional wood modifier.