We report a facile fractionation strategy using choline hydroxide (ChOH) based alkaline deep eutectic solvents (DES) for whole-component upgrading of bagasse. Through selective lignin and xylan dissolution, along with extensive biomass swelling, high-value lignin-carbohydrate complexes (LCC, with high β-O-4 bond content of 68.9/100 Ar) and high-purity xylan were extracted without compromising cellulose recovery and hydrolysis. This work provided the key to solving the technical contradiction between cellulose availability and lignin structural integrity.