Mechanical pretreatment on brewer's spent grain( BSG) can change its physical structure,make the anti-nutritional factors easily be degraded,increase the bioavailability and improve the feeding quality. The particle sizes of BSG after pretreatment by blade grinding and ball milling were distributed in the range of 300 ~ 1 000 μm and 10 ~ 200 μm respectively. Compared with untreated BSG,the total soluble sugar contents of BSG were respectively increased by 2. 2 times and 1. 7 times,and reducing sugar contents were respectively increased by 40% and 18. 9% after ball milling and blade grinding. With enzymatic hydrolysis of BSG after ball milling and blade grinding by cellulase and neutral protease,the total soluble sugar contents were increased by 2. 5 fold and 1. 7 fold,reducing sugar contents were increased by 2. 2 fold and 1. 4 fold,soluble protein contents were respectively increased by 1. 8 and 1. 4 fold,polypeptide contents were respectively increased by 2. 2 and 1. 2 fold compared to those of BSG after enzymatic hydrolysis without mechanical treatment. The efficiency of enzymatic hydrolysis of BSG after ball milling was higher than that of BSG after blade grinding. After blade grinding with sieving,the enrichment and isolation of protein-fiber could be preliminarily obtained in our work.