The invention relates to an antibiosis acrylic fiber and a preparation method thereof. Firstly, an acrylic fiber spinning solution is extruded by a spinning nozzle, solidified, stretched by a water bath and washed to obtain fibers, and the fibers are dipped into solution which contains an organic antibacterial agent and is subjected to thermal stretch and postprocessing to obtain the antibiosis acrylic fiber. Finally, a product mainly consists of the acrylic fiber and the organic antibacterial agent, the acrylic fiber and the organic antibacterial agent are combined through an ionic bond and/ or hydrogen bond; the content of the organic antibacterial agent in the product is 0.2-0.5wt%, the antibacterial rate for staphylococcus aureus, colibacillus and candida albicans is greater than or equal to 99%, the antibacterial rate after washing is carried out for 50 times is greater than or equal to 99%, a filament number is 0.5-5.0dtex, breaking strength is 2.0-.2cN/dtex, the antibiosis acrylic fiber is the short fiber, filament or tow, and the antibiosis acrylic fiber is applied to fields including pure spinning yarns, commingled yarns, knitted fabric, woven fabric or nonwovens. The preparation method for the antibiosis acrylic fiber has the advantages of simple technology, low cost and convenience and flexibility in operation.