In this study, the alkaline catalyst (NaOH)-aided sulfolane organosolv pretreatment was first developed to reduce the recalcitrance of willow (Salix matsudana cv. Zhuliu) for effective saccharification and lignin valorization in subsequent processes. The pretreatment notably removed lignin, minimized cellulose loss, and increased the accessibility of cellulose. The sulfolane/water (50/50, w/w) pretreatment with 4% NaOH at 140 degrees C for 1.5 h increased the glucose saccharification yield by 14.2-fold of the yield from the untreated willow. The recovered lignin had high purity (similar to 97.0%), well-preserved molecular weight (4300-5010 g/mol), and low polydispersity (similar to 2.0). NMR analysis of the recovered lignin also indicated that it retained the representative linkage structures (e.g., beta-O-4, beta-beta linkages). Based on these observations, the recovered lignin showed great potential as an intermediate in the production of functional biomaterials and/or green biofuels.