Abstract: The process in the transformation of lignocellulose to ethanol is mainly composed of four steps，Such as pretreatment，hydrolysis，fermentation and purification. Since industrial application of microorganisms has great advantages in reducing the cost of production，this review herein focuses on the research progress in the application of microorganisms in pretreatment，cellulase production and ethanol fermentation. Furthermore，both challenges and progresses in the whole process are briefly introduced，such as the optimization of some process parameters，enhancement in the production and activity of cellulase，and microorganisms genetically engineered to metabolize both hexose and pentose.