Abstract: Against the backdrop of the rapid development of modern animal husbandry,the breeding industry of laying hens still faces many challenges,among which intestinal diseases are particularly prominent.Although traditional antibiotic treatment can control the disease to a certain extent,the ensuing problems of increased bacterial resistance,imbalance of intestinal flora,and increased treatment costs should not be ignored.Therefore,it is crucial to explore new products that are safe and effective and can replace antibiotics for the sustainable development of the breeding industry of laying hens.Bacillus subtilis is a Gram-positive non-pathogenic Bacillus with strong resistance.It can be used as a green and residue-free probiotic additive in the breeding industry of laying hens.The bacteria can effectively colonise the intestinal tract of laying hens,inhibiting the growth of pathogenic bacteria and promoting the growth of beneficial bacteria.It can maintain the balance of intestinal flora in laying hens.At the same time,it can enhance the immunity of laying hens by increasing the level of antibody and maintain the intestinal health.In addition,Bacillus subtilis can maintain the intestinal morphology and structure of laying hens by increasing the villi height and decreasing the crypts depth.In the practice of laying hens,the application of Bacillus subtilis can significantly enhance the performance,including the improvement of egg quality,the increase of egg production,and the reduction of the feed-to-egg ratio.The author reviewed the biological characteristics of Bacillus subtilis,its mechanism of action in the intestinal tract and the application effects of different strains of Bacillus subtilis in laying hens，to provide a reference basis for the subsequent development and utilisation of Bacillus subtilis for feeding.

Key words: Bacillus subtilis; laying hens; intestinal health