Abstract: The disclosure relates to a method for preparing unbleached biomechanical pulp by hot steam and biological enzyme treatment and full utilization of by-products thereof, and belongs to the technical field of papermaking technology and comprehensive utilization of waste. The present disclosure proposes a method for preparing high-strength unbleached biomechanical pulp, using whole wheat straw as a raw material, by using hot water in coordination with an alkaline biological enzyme to treat whole wheat straw, thereby meeting the requirements for the production of unbleached linerboard and paper-based materials, and recycling by-products thereof to prepare biomass compound fertilizers, which creates wealth from solid waste and realizes the high-value full utilization of wheat straw. The preparation method of the disclosure is simple, green, clean and efficient, and has good practical application value and broad application prospects.