The invention discloses Chuqinan for preventing and treating piglet colibacillosis and a preparation method thereof. The Chuqinan is prepared from the following ingredients in parts by weight: 20 to 40 parts of pure natural garlicin emulsifying agents, 30 to 50 parts of galic essential oil, 5 to 10 parts of radix gentianae scabrae bunge, 5 to 12 parts of rhizoma coptidis, 3 to 12 parts of cortex phellodendri, 2 to 8 parts of prepared rehmannia roots, 2 to 8 parts of rhizoma et folium eupatorii japonici, 5 to 15 parts of raw liquorice roots, 5 to 18 parts of dark plum, 4 to 13 parts of fructuscrataegi, 2 to 9 parts of cercis leaves, 1 to 7 parts of aloe, 2 to 10 parts of radix scrophulariae, 10 to 20 parts of herba menthae, 5 to 12 parts of honeysuckle flowers, 4 to 10 parts of fructus forsythia and 10 to 20 parts of herba houttuyniae. The preparation method is simple; the prepared Chuqinan can inhibit and kill various pathogenic bacteria; the gastrointestinal motility and the gastrointestinal fluid secretion can be effectively promoted; the diseases of the digestive system are prevented; the feed conversation and utilization is promoted; the benefits of breeding industry are improved.