In order to further explore the changes of free total phenols content and lignin exposure after AFEX pretreatment and their effects on enzymatic hydrolysis, AFEX pretreatment experiments were conducted on corn stover（CK）under two conditions: L-AFEX (1g/g, 60% moisture content, 90℃, 5min) and H-AFEX (1g/g, 60% moisture content, 140℃, 15min). The changes of lignocellulosic composition, content of free total phenols, and exposure of cellulose and lignin of CK, L-AFEX pretreated corn stover, and H-AFEX pretreated corn stover were systematically characterized, and their effects on enzymatic hydrolysis were analyzed. The results showed that L-AFEX and H-AFEX enhanced the glucose yield of enzymatic hydrolysis of corn stover to 37.57% and 74.74%, respectively. As the condition of AFEX pretreatment was increased, the content of cellulose and hemicellulose in corn stover remained unchanged, the content of acid soluble lignin was increased, the hydrophilicity of lignin was enhanced which might weaken the non-productive adsorption between lignin and cellulase during enzymatic hydrolysis, and more phenols were produced. The inhibition effects of the phenols produced during AFEX pretreatment on cellulase hydrolysis ability were significant (4.10% for L-AFEX and 10.40% for H-AFEX). Moreover, the enzymatic hydrolysis of H-AFEX-pretreated solid residue was inhibited (5.06%) by phenols. After AFEX pretreatment, the cell wall structure was destroyed, the enzyme-accessible surface area was increased, surface area of cellulose was increased from 316.08m2/g (CK) to 430.97m2/g (L-AFEX) and 422.27m2/g (H-AFEX), surface area of lignin was decreased from 293.13m2/g (CK) to 271.25m2/g (L-AFEX) and 215.23m2/g (H-AFEX), and the ratio of cellulose surface area to lignin surface area was increased from 1.08 (CK) to 1.59 (L-AFEX) and 1.96 (H-AFEX), which effectively reduced the steric hindrance of lignin and enhanced the enzymatic hydrolysis efficiency.