In order to improve the yield of ethanol,the lactate dehydrogenase in a key branch of Thermoanaerobacterium aotearoense was deleted via the homologous recombination,and the thermophilic and anaerobic metabolic engineered Thermoanaerobacterium aotearoense,namely Δldh mutant was screened.Then,glucose fermentation,xylose fermentation and glucose/xylose co-fermentation of Δldh mutant and the wild strain were respectively performed to produce ethanol.The results indicate that（1） as compared with the wild strain,Δldh mutant is of higher ethanol yield and rapid suger consumption;（2） both the Δldh mutant and the wild strain grow well on glucose and xylose;（3） as compared with sole xylose fermentation,a xylose restraining may occur during the glucose/xylose co-fermentation;and（4） when glucose is used as the sole carbon source,both the mass concentration and the yield of ethanol reach the maximum values,namely 25.93g/L and 0.39g/（L·h）,respectively.