An integrated process to increase the yield of incomplete degradation products of galactomannan (GalM) especially for galactomanno-oligosaccharides (GalMOS) was suggested. Trichoderma reesei employed Avicel or GalMOS as a carbon source to produce beta-mannanase or alpha-galactosidase independently, with a result of 3.78 +/- 0.12 U/mL of beta-mannanase activity and 2.45 +/- 0.06 U/mL of alpha-galactosidase activity which were obtained, respectively. GalM in Sesbania seed was hydrolyzed simultaneously by a mixture of crude enzyme with beta-mannanase and alpha-galactosidase at a dosage of 20 U/g GalM and 15 U/g GalM, respectively; the yields of incomplete degradation products of GalM (IDP-GalM) and GalMOS were 78.84% +/- 3.14% and 30.94% +/- 0.38%, respectively, which was beneficial to improve the biological activity of the incomplete degradation products. The role of alpha-galactosidase addition in mixture enzymes is to remove the galactose substituents from mannan backbone of GalM and alleviate the steric hindrance of beta-mannanase hydrolysis.