NOVELTY - Microbial inoculum complex mixture comprises 50-70 %mass microbial inoculum I, and microbial inoculum II, where the microbial inoculum I comprises Trichoderma, Penicillium, Aspergillus and Actinomyces, and the microbial inoculum II comprises beer yeast, Hansenula and Candida.    USE - The microbial inoculum complex mixture is useful for producing ethanol (claimed).    ADVANTAGE - The microbial inoculum complex mixture has excellent stability to dissolve cellulose, and is easy to recycle. The method requires simple device, is simple and environmentally-friendly, and increases biomass resource utilization rate.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) method for preparing the above-mentioned microbial inoculum complex mixture, involves inoculating each of the above-mentioned strains in corresponding culture medium, shaking the cultures at 40 degrees C and 170 revolutions per minute (rpm) for 36-72 hours and diluting each single strain, and (b) mixing the above-mentioned microbial inoculums I and II; and    (2) method for producing ethanol, involves (a) crushing straw to fine particles having particle diameter of 0.5-0.8 cm, (b) soaking the crushed straw in ionic liquid comprising 1-allyl-3-methylimidazolium acetate for 5-6 hours in a mass ratio of 1:20-25, (c) centrifuging the above-mentioned mixture at 12000 rpm for 10 minutes, collecting supernatant and subjecting the supernatant to solid-liquid separation, (d) mixing supernatant and nutrient solution in a volume ratio of 1:5-10, uniformly blending the mixture, separating aqueous phase from the ionic liquid phase, and taking the aqueous phase as fermentation substrate, (e) spraying the fermentation substrates into mixture into a microbial inoculum complex mixture in a mass ratio of 3-7:1, where the microbial inoculum complex mixture comprises 3x 107 colony-forming unit (cfu)/ml to 5x 108 cfu/ml, and (f) fermenting the mixture for 12-24 hours, filtering the fermented mixture and subjecting the filtrate to rotary evaporator at 78 degrees C and vacuum distillation.