Experiments were carried out on the conditions of bioethanol production from wheat straw through simultaneously saccharification and fermentation using Saccharomyces cerevisiae BY4742.The effects of temperature,solid content,enzymeloading and yeast concentration on concentration and yield of ethanol in the SSF processes were systematically investigated.These parameters were further optimized to increase the final concentration and yield of ethanol.The results showed that the optimum conditions for SSF of wheat straw were as follows: temperature 38℃,solid content 16.0%(w/v),enzyme loading 35 FPU/g and substrate and yeast concentration 8 g/L.The maximum ethanol concentration reached 38.32 g/L,which was equivalent to 71.71% of the theoretical ethanol yield,with xylose concentration of 12.94 g/L obtained after 120 h SSF of NaOH pretreated wheat straw under the optimized conditions.