To convert corn stover to fermentable sugar efficiently and improve the competiveness of cellulosic ethanol, the optimal process of semi-simultaneous saccharification and fermentation (SSSF) for corn stover to produce fuel ethanol based on the alkaline hydrogen peroxide (AHP) pretreatment was investigated. The optimal biomass loading was confirmed by the relationship of biomass loading and sugar yields. Also, the optimal addition of Tween 20 was studied by adding it to AHP pretreated corn stover during enzymatic hydrolysis. The results showed that the optimal condition for enzymatic hydrolysis were as follow: 200 g/L of biomass loading and 8% (ω) of Tween 20 loading. Based on this condition, some parameters were investigated, the optimal conditions for SSSF were as follows: 5%(ω) of Tween 20 loading, the seed age of yeast was 16 h, the ending time of pre-enzymatic hydrolysis during SSSF was 10 h, the fermentation temperature was 34 ℃, and the time of SSSF was 7 d. Under these conditions, the final concentration of ethanol was 23.64 g/L, and the conversion rate was 76.54%. Compared to the control (without addition of Tween 20), the ethanol yield was improved by 3.41%. The results indicated that converting high solids corn stover could be converted to fermentable sugar and ethanol efficiently under this process. This study provided an efficient way for the industrial-scale production of cellulosic ethanol.