Trichoderma reesei is an important microbe in biomass hydrolysis but is characterized by its inability to remove acetylated glucomannan. To improve the saccharification efficiency of T. reesei, an acetyl xylan esterase (AXE) gene from Aspergillus oryzae was successfully overexpressed by fusing with xynlanase 2 (Xyn2) from T. reesei as a carrier protein. The production of AXE in the selected transformant T2 was 11.04 U/ml, which was approximately 74% higher than that of the parent strain. The molecular mass of recombinant AXE (rAXE) on SDS-PAGE was about 35 kDa. The saccharification efficiency of rAXE from T. reesei Rut-C30 was better than that of the parent strain and resulted in approximately 23.2%, 22.7%, and 19.4% higher yield of reducing sugar in paddy straw, corn stover plus paddy straw mix (1:1 ratio), and corn stalk (delignified) hydrolysis, respectively. This result demonstrates that the expression of heterogenic accessory enzymes in T. reesei may be an alternative approach to improve the ability of the enzyme complex to decompose lignocellulose.