The invention discloses lactobacillus plantarum, a feed premix containing the lactobacillus plantarum and a preparation method of the lactobacillus plantarum. The preservation number of the lactobacillus plantarum is CGMCC No.9642. The feed premix disclosed by the invention is prepared from a composite culture solution which is compounded by whey powder, cane sugar, a herba portulacae extract, a rhizoma smilacis glabrae extract, an astragalus membranaceus extract and a humifuse euphorbia herb extract as a culture medium in a manner of anaerobic fermentation. The feed premix contains abundant active polysaccharides, flavones, viable bacteria and metabolites thereof; the feed premix is used as a microecological feed premix for farming prawns; growth of enteric pathogenic bacteria can be inhibited by the viable bacteria and metabolic lactic acid thereof; the metabolites of the active polysaccharides, the flavones and the viable bacteria are relatively easily absorbed by shrimps; and the multi-effects of the viable bacteria, the active polysaccharides and the metabolites can be put in an effective play.