Rapeseed straw was used as raw material to investigate the changes in the lignocellulosic components, types and contents of degradation products after different absorbed doses of ⁶⁰Co-γ-ray irradiation, and the enzymatic hydrolysis and fermentation characteristics were evaluated in this research. The results showed that the contents of cellulose, xylan and lignin decreased, the total amount of water-soluble components increased, and the pH of water extract gradually decreased in the rapeseed straw with the increase of irradiation absorbed dose. The total amount of four types of small molecular fatty acids in the degradation products of rapeseed straw gradually increased with the irradiation absorbed dose increasing, reaching a maximum of 9.25 mg/g after 1 000 kGy irradiated. The total amount of nine types of small molecular aromatic degradation products first increased and then decreased, reaching a maximum of 0.22 mg/g in 800 kGy irradiated rapeseed straw. The cellulose conversion rate and glucose concentration of rapeseed straw by enzymatic hydrolysis increased with the increase of irradiation absorbed dose. The cellulose conversion rate decreased and the glucose concentration in enzymatic hydrolysate gradually increased with increasing substrate concentration. The cellulose conversion rate for enzymatic hydrolysis was 57.55% and ethanol conversion rate was less than 10% of 800 kGy irradiated rapeseed straw at 15% substrate concentration in separate hydrolysis and fermentation. Irradiation combined with water extraction significantly improved the enzymatic and fermentation efficiency of rapeseed straw. The cellulose conversion rate and glucose concentration for enzymatic hydrolysis were 71.62% and 40.38 mg/mL, respectively, the ethanol conversion rate was 64.00% after 48 h of separate fermentation, and the glucose in fermentation broth was completely consumed for 800 kGy irradiated rapeseed straw after water extraction at 15% substrate concentration.