The alkaline-pretreated wheat straw was used as raw materials, and the fed-batch simultaneous saccharification and fermentation (SSF) process for ethanol production with higher substrate loading (up to 16% (w/v)) was investigated. Firstly, the Fed-batch SSF with different feeding strategy was optimized. The highest ethanol concentration reached to 37.9 g/L with an initial substrate loading of 10% (w/v), and equal substrate addition (3%) at 8h and 16h respectively. Then the effects of Tween-20 were also investigated. The results showed that Tween-20 addition with 2.0 g/L can improved the ethanol production. Furthermore, a nonisothermal fed-batch SSF was proposed, and the ethanol concentration of 41.5 g/L, corresponds to 81.0 % of the theoretical yield was achieved within 72 h.