Abstract: Dilute sulfuric acid pretreatment of paulownia before cellulose enzymatic hydrolysis was investigated. The biomass with a 10% solid loading rate was pretreated at 121℃ by dilute sulfuric acid with different concentrations (0.5%, 1.0%, 1.5% and 2.0%) for 30, 60 and 90 min. The concentrations of the total reducing sugars, monosaccharides and inhibitors (e.g. furfural and HMF(5-hydroxymethylfurfural)) in the pre-hydrolyzate were analyzed to obtain the optimum acid hydrolysis condition that did not affecting the flowing enzymatic hydrolysis. The total reducing sugar yield was about 82% of the theoretical maximum value, and the conversion efficiencies for glucan and xylan were 39.5% and 48.7%, respectively, when the biomass was pretreated by 1.5% sulfuric acid for 60 min.