The invention discloses an astragalus membranaceus micro-ecologic preparation as well as a preparation method and an application thereof, and belongs to the technical field of feed additives and biological fermentation tradition Chinese medicines. The micro-ecologic preparation is prepared by fermenting astragalus membranaceus, a lactic acid bacteria seed solution and a solid culture medium, wherein the lactic acid bacteria seed solution is prepared by mixing and culturing enterococcus faecium and lactobacillus plantarum at a ratio of (2-8): (8-2); the number of viable organisms in the inoculated lactic acid bacteria seed solution, corresponding to every 25-75 g of astragalus membranaceus, is 25*109; compared with the traditional additive which directly mixes the lactic acid bacteria and the astragalus membranaceus, the astragalus membranaceus micro-ecologic preparation has the effect that the yield of the crude polysaccharide and the quantity of the lactic acid bacteria are improved after fermentation. According to the preparation method of the astragalus membranaceus micro-ecologic preparation, the synergistic effect of the lactic acid bacteria and the astragalus membranaceus is improved by selecting proper fermentation temperature and fermentation time. The astragalus membranaceus micro-ecologic preparation is used as a livestock feed additive.