The invention is prepared by dewatering and drying garlic straw, chopping, wind screening, grinding, ultra-finely grinding and sterilizing. Duo to increased surface area and improved surface activity, prepared garlic straw ultra-fine powder product increases biological availability, fully improves product usage effect, enlarges application range, and can be widely applied in cooperation particle forage, concentrated forage and additive premix of livestock, poultry and aquatic product culture. Duo to sterilization treatment in production process, the invention can store the fine power for a long period, is favourable to enterprise large-scale production and application, and solves problems that application effect of simple grinding is not ideal and industrialization is not realized.