The invention relates to a preparation method for a density-controllable light bamboo-wood-based fiber plate. The method comprises the steps that firstly, thermosetting phenolic resin is prepared; secondly, bamboo powder phenolic resin composite foam particles are prepared, then, fir wood fiber, paraffin and the bamboo powder phenolic resin composite foam particles are placed into a mixer, next, amodified urea-formaldehyde resin adhesive is sprayed, and paving is performed after the mixture is uniformly stirred; thirdly, the mixture is placed into a pre-presser for prepressing, and then the product is moved into a hot press to be subjected to hot-pressing treatment; and finally, the product is subjected to pressure relief, cooling, plate cutting and maintenance, and the density-controllable light bamboo-wood-based fiber plate is obtained. According to the method, bamboo powder and the phenolic resin are processed into a foam particle composite system by means of the special treatmenttechnology, and the foam particle composite system is used for replacing a part of layer structures of the fiber plate material; and the purpose of weight reduction is achieved by enhancing the porosity of the original material system, the complexity of the processing technique is effectively lowered, and the controllability of the processing technique and the regulation of the product density areimproved.