Sequential Fenton oxidation (FO) and hydrothermal treatment were performed to improve the effect of pretreatment and enzymatic hydrolysis of mixed hardwood. The molar ratio of the Fenton reagent (FeSO4.7H(2)O and H2O2) was 1: 25, and the reaction time was 96 h. During the reaction, little or no weight loss of biomass was observed. The concentration of Fe2+ was determined and was found to increase continuously during FO. Hydrothermal treatment at 190-210 degrees C for 10-80 min was performed following FO. Sequential FO and hydrothermal treatment showed positive effects on pretreatment and enzymatic hydrolysis. Xylose concentration in the hydrolysate was as high as 14.16 g/L when FO-treated biomass was treated at 190 degrees C, while its concentration in the raw material was 3.72 g/L. After 96 h of enzymatic hydrolysis, cellulose conversion in the biomass obtained following sequential treatment was 69.58-79.54%. In contrast, the conversion in the raw material (without FO) was 64.41-67.92%. (C) 2015 Elsevier Ltd. All rights reserved.