Abstract: Green liquor consists of sodium carbonate and sodium sulfide and is readily available in any kraft mill. Effects of refining on improving enzymatic hydrolysis was investigated using green liquor pretreated mixed hardwoods at 12% total titratable alkali charge. The sugar yield increases with the PFI revolution. Adding 1% NaOH during refining did not affect on pulp freeness significantly, but could effectively improve the sugar yield of enzymatic hydrolysis. Compared with controlled green liquor pretreated pulp without refining, a remarkable increase in sugar yield was achieved at a low enzyme loading after the pulp was refined by a PFI mill. Meanwhile, an obvious increase in sugar yield could be obtained in the initial 6 or 12 h of enzymatic hydrolysis with the same cellulase loading after pulp refined by PFI mill. The results indicate that refining has a great feasibility for increasing the accessibility of the cellulose and improving the enzymatic hydrolysis of lignocellulosic biomass.