NOVELTY - Method for preparing bioethanol involves (a) pretreating lignocellulose, (b) mixing lignocellulose with nutrient liquid to obtain mixture A, (c) adding cellulase, performing pre enzymatic hydrolysis, adding recombinant Saccharomyces cerevisiae yeast secreting beta -glucosidase, fermenting, performing solid-liquid separation, (d) adding pretreated lignocellulose, performing solid-liquid separation, and mixing solid in nutrient liquid to obtain mixture B, (e) adding beta -glucosidase, and performing fermentation reaction, and (f) repeating steps (d) and (e).    USE - The method is useful for preparing bioethanol, and improving cellulase enzyme recovery (claimed).    ADVANTAGE - The bioethanol production method is simple, easy and cost-effective.    DETAILED DESCRIPTION - Method for preparing bioethanol involves (a) crushing lignocellulose, pretreating the crushed lignocellulose, and drying pretreated lignocellulose at low temperature, (b) mixing 2.5-10 g lignocellulose obtained in step (a) with 50 ml nutrient liquid to obtain mixture A, (c) placing mixture A in a reactor at 45-50 degrees C, calculating the quantity of cellulose in lignocellulose, adding 10-50 filter paper unit (FPU) cellulase to 1 g lignocellulose, performing pre enzymatic hydrolysis for 12-24 hours, cooling to 30-37 degrees C, adding recombinant Saccharomyces cerevisiae yeast secreting 1-5 g/l beta -glucosidase, fermenting the mixture at 30-37 degrees C for 72-168 hours, performing solid-liquid separation to obtain fermented liquid and fermented residue, (d) adding pretreated lignocellulose obtained in step (a) to the fermented liquid obtained in step (c) by absorbing at 4-25 degrees C for 60-120 minutes, performing solid-liquid separation to obtain liquid and solid, where the liquid is separated by rectifying ethyl alcohol, and uniformly mixing the solid in nutrient liquid obtained in step (b) to obtain mixture B, (e) placing the mixture B in a reactor at 45-50 degrees C, adding beta -glucosidase, calculating the quantity of cellulose in lignocellulose, adding 0-35 cellobiase units (CBU) beta -glucosidase to 1 g cellulose, adding suitable quantity of beta -glucosidase enzyme to the fermented liquid obtained in step (c), adding cellulase in a weight ratio of not less than 0.7, performing reaction at 45-50 degrees C for 12-24 hours, cooling at 30-37 degrees C, and performing fermentation reaction as mentioned in step (c), and (f) repeating steps (d) and (e).