The invention discloses a preparation method for a biomass photoelectric material, and belongs to the technical field of the photoelectric material preparation. The preparation method comprises the following steps: boiling roxburgh rose dry powders and filtering, collecting filtrate and residue, mixing the leach liquor after extracting the residue with the filtrate and spin-steaming, obtaining concentrated solution, reacting the concentrated solution with silane coupling agent KH-550 so as to prepare reaction liquid, drying the reaction liquid after centrifuge and dialysis treatments, obtaining a dry material for future use, using rice husk for pulping and obtaining rice husk serous fluid, using hydrochloric acid to adjust pH and adding yeast powder for fermenting, obtaining a fermenting material, drying the fermenting material, roasting, grinding the fermenting material to be powder, obtaining the powder, and mixing the powder with the dry material, adding absolute ethyl alcohol, drying a reagent after the stirring reaction, and obtaining the biomass photoelectric material. The prepared biomass photoelectric material has excellent conductivity, good material stability during the photoelectricity information conversion, and high electrochromism response sensitivity, and is suitable for large-scale popularization and application.