The invention discloses an anisotropic wood-based nanofiber aerogel. The aerogel is obtained by the following steps: light wood with a density of 80-150 mg/cm<3> is adopted, delignification treatmentis performed, dehemicellulose treatment is performed to prepare a wood-based nanofiber hydrogel, water in the hydrogel is replaced to obtain a nanofiber alcohol sol, freeze drying is performed, and therefore the aerogel is obtained. The invention also discloses the specific preparation method. According to the method provided by the invention, the wood-based nanofiber aerogel prepared by the method has a low density, high porosity, good compression performance and elasticity, is a green environmentally-friendly aerogel material, has low preparation costs, can be produced in a large scale, andhas board application prospects in the fields of thermal insulation, noise insulation, adsorption catalysis, biomedicine, energy storage and the like.