TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: The method further comprises pre-fermenting the sugar juice with 20-40% concentrated sugar by adding activated yeast in disinfected fermentation tank; regulating the quantity of yeast in yeast tank by the new activated yeast, where concentration of yeast is not less than 500000000/ml; adding sweet sorghum stalk sugar liquid at 200 L/hour and air flow rate of 550 L/minute; controlling the temperature at 32.5 degrees C; regulating the air flow rate at 800 L/minute; and stirring for 25 minutes at 100 revolutions/minute. It further comprises fermentation comprising adding the sweet sorghum stalk sugar liquid continuously, where air flow rate is increased to 800-1200 L/minute; continuously carrying out stirring; controlling the pH within 4.0 plus minus 0.1 for 1.5-2 hours until fermentation is finished, where air feeding is stopped, 3-4 hours after fermentation is finished, continuous addition of sweet sorghum stalk sugar liquid is stopped after 6-7 hours of fermentation, and fermentation is stopped after 25-35 hours; and separating, reclaiming, and activating yeast by separating the yeast in fermentation liquid by disc separator, dipping the separated yeast liquid in diluted acid liquid with 1% concentration, and keeping temperature within 32-35 degrees C for 5 minutes, where separated and activated yeast is reused for 3-4 times. The yeast is Candida tropicalis ZXNY-1 (CGMCC 3889). The sweet sorghum stalk sugar liquid is the sweet sorghum stalk sugar juice with sugar content of 20-45%, which is prepared into sugar liquid with 20-30 g/ml main sugar and 4 pH, before the step of pre-fermentation. The unfreezing method comprises spraying water with temperature of 75-80 degrees C or squeezed sweet sorghum stalk sugar juice with same temperature on the torn and crushed sweet sorghum stalk. Five groups of three-roller squeezers are used for squeezing in juice extraction step, where pressure of the pressure rollers is 13-15 MPa, the amount of permeation water added is 20-30% (based on the stalk), and the temperature of permeation water is 75-80 degrees C. The method further comprises distilling the fermented yeast liquid by ethanol and dehydrating by ethanol to prepare fuel ethanol. It comprises distilling fermented yeast liquid in rough distillation tower, where content of ethanol is 60 vol./vol.% based on the rough distillation tower; finely distilling the crude alcohol solution with ethanol content of 60% in the fine distillation tower; and dehydrating the alcohol solution by molecular sieve to obtain fuel ethanol with ethanol content of 99.5%.