The invention discloses a cellulose fiber-supported nano silver antibacterial material and a preparation method thereof. The preparation method comprises the steps of: conducting chemical pretreatment on cellulose fibers, then conducting TEMPO (2, 2, 6, 6-tetramethylpiperidine-1-oxyl) selective oxidization on the cellulose fibers, and finally on the premise that not any reducing agent is added, enabling the oxidized cellulose fibers to react with silver nitrate in silver nitrate water solution through a short-time microwave heating method to prepare the cellulose fiber-supported nano silver antibacterial material with small-diameter and even-structure nano silver particles. By adopting the preparation method, on the premise that not any reducing agent is added, in-situ reduction and growth of nano silver on carboxylated cellulose fiber supporters are realized. The prepared cellulose fiber-supported nano silver antibacterial material has the advantages of small nano grain size and even size, and can be widely applied to the fields of antibacterial operation clothes, wound dressing, drug controlled release, textile coating and the like.