The invention discloses an alliin-based antibiotic-replacement feed synbiotic composition, and relates to an alliin-based antibiotic-replacement feed synbiotic composition and a preparation method thereof. The allicin is allicin which is obtained through natural fermentation treatment and contains stable sulfide components, and comprises diallyl disulfide (DADS) and diallyl trisulfide (DATS). Theprobiotics is selected from one or combination from lactic acid bacteria and bacillus licheniformis; bacillus subtilis, bifidobacterium bifidum, enterococcus faecalis, enterococcus faecium, lactobacillus acidophilus, lactobacillus casei, lactobacillus plantarum, pediococcus pentosaceus, the invention discloses rhodopseudomonas palustris. The composition is one or a combination of more of bifidobacterium infantis, bifidobacterium longum, bifidobacterium breve, bifidobacterium animalis, bifidobacterium adolescentis, streptococcus thermophilus, lactobacillus reuteri, aspergillus niger, aspergillus oryzae, bacillus tarda, bacillus pumilus, lactobacillus cellobiosus, lactobacillus fermentum, lactobacillus bulgaricus, lactobacillus buchneri and bacillus laterosporus. The method is used for special breeding environments with aseptic requirements, improving the water source environment of farms and the like.