The invention discloses a method for preparing fewer-layer graphene on the basis of biomass waste, which comprises the following steps: carrying out hydrothermal treatment on the biomass waste, and carrying out carbonization by heating and calcination, thereby obtaining a carbonization material; immersing the carbonization material in an acid solution to remove impurities, thereby obtaining biomass carbon; and quickly heating the biomass carbon in an argon atmosphere, and carrying out high-temperature graphitization to obtain the biomass fewer-layer graphene. The hydrothermal process is combined with the high-temperature graphitization to directly strip the biomass waste, and the carbonization and high-temperature graphitization are carried out. Thus, the prepared biomass fewer-layer graphene has the advantages of fewer layers (2-10 layers), fewer defects, fewer oxy groups, high electric conductivity and small carbon layer interval. The method is simple to operate, has the advantages of low cost and high graphene yield, and can easily implement industrialized large-scale production. The prepared biomass fewer-layer graphene can be used in the fields of lithium ion batteries, supercapacitors and the like, is beneficial to green production of battery industry, and has important practical value and favorable application prospects.