To improve the chemical pretreatment efficiency of bio-ethanol, a photocatalyst assisted alkaline approach was developed to remove lignin structure and increase the amount of fermentable component in lignocellulosic biomass (corn stover). Two kinds of base tested in this study were aqueous ammonia and sodium hydroxide, respectively. Due to the high volatility, a special experimental design was used in ammonia pretreatment, which limited the UV penetration, hence only moderate improvement on enzymatic digestibility of the treated biomass could be obtained through the photocatalyst-assisted photodegradation. Meanwhile, testing with sodium hydroxide yielded elevated delignification result and confirmed that the UV penetration played an essential role in photocatalytic treatment.