NOVELTY - Co-producing fuel ethanol and lignin comprises e.g. (1) crushing sweet sorghum stems, regulating a moisture content of the stem, inoculating yeast and regulating temperature, (2) spraying alkali solution, heating and distilling, collecting a condensate, using residual solid phases as distillation materials, (3) rinsing the materials and performing solid-liquid separation to delignification residues of the solid phase, (4) rinsing the residues as an enzymolysis substrate, adding enzyme to an enzymolysis buffer solution to obtain an enzymolysis mixed solution, and (5) inoculating yeast.    USE - The method is useful for co-producing fuel ethanol and lignin.    ADVANTAGE - The method is capable of rapidly and economically co-producing fuel ethanol and lignin with less energy consumption.    DETAILED DESCRIPTION - Co-producing fuel ethanol and lignin comprises (1) crushing sweet sorghum stems, regulating a moisture content of the stem to 60-80%, inoculating yeast according to a mass ratio of the sweet sorghum stems to the yeast culture solution of 1 kg:(100-200) ml, regulating temperature in a fermentation tank at 25-35 degrees C and controlling the revolution speed of the fermentation tank at 0.1-1 Revolutions per minute for 18-42 hours, (2) spraying 5-25 ml of 0.5-10.0 mole/l of alkali solution at every 50 g of fermentation materials, heating up and distilling the mixture, collecting the condensate, stopping collecting when a volume of the collected condensate is one half of the mass of the added fermentation materials and using the residual solid phases as distillation materials for opening a lignocellulose structure, (3) rinsing the alkali distillation materials and then performing solid-liquid separation to obtain alkali lignin of the liquid phase and delignification residues of the solid phase, (4) rinsing the delignification residues as the enzymolysis substrate (5-30 wt.%), adding an enzymolysis buffer solution, adding enzyme for performing enzymolysis, where a pH value of the enzymolysis liquid is 4-6, adding the enzyme to the enzymolysis buffer solution in an amount of 5-30 FPU/g of the substrate and performing enzymolysis at 45-55 degrees C for 24-120 hours to obtain an enzymolysis mixed solution, and (5) inoculating the yeast to the enzymolysis mixed solution for fermentation, where the enzymolysis mixed solution is sterilized at 115-121 degrees C for 10-20 minutes, and then fermenting the yeast (5-10 vol.%) in the fermentation tank at 25-35 degrees C for 20-42 hours to obtain the ethanol solution.