The invention discloses a preparation method of a highly antibacterial alginate dressing, and belongs to the technical field of preparation of medical dressings. The preparation method comprises the following steps: oxidizing sodium alginate by virtue of sodium periodate, and mixing silver nitrate, zinc nitrate, a trisodium citrate solution and the like so as to obtain a silver-zinc antibacterial agent; then, combining dopamine hydrochloride and the oxidized sodium alginate, wherein the dopamine hydrochloride is attached to the surface of the oxidized sodium alginate through a dopamine polymerization reaction, and on the basis of reducing and chelating effects of the dopamine on silver and zinc irons, silver and zinc are uniformly loaded on the surface of the oxidized sodium alginate by virtue of a method of conducting in-situ reduction on the silver and zinc irons, so that a spinning solution is prepared; and conducting vacuum deaerating, spinning, coagulating, stretching, rinsing, rolling and drying, and making the dressing by virtue of a needle punching technology, so that the highly antibacterial alginate dressing is obtained. The alginate dressing prepared by the invention is excellent in hemostatic and antibacterial effects, the alginate dressing is good in hygroscopic swelling performance and the alginate dressing is capable of effectively protecting wounds and accelerating healing speed of the wounds; and dressing fibers are closely combined, and the alginate dressing is relatively good in mechanical performance and convenient to change.