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To address the demand for sustainable, sulfur-free fractionation, this study investigated the alkali-ethanol fractionation of Miscanthus × giganteus using sequential Response Surface Methodology (RSM) strategy to systematically quantify parameter interactions and optimize process performance. An initial Box-Behnken Design (BBD) was employed at low severity to screen four independent variables (temperature, time, alkali concentration and ethanol concentration), regarding their impact on pulp yield, pulp chemical composition, and xylan solubilization. Subsequently, a Central Composite Design (CCD) was used to optimize the principal process drivers (temperature and alkali concentration) at high severity. In both designs, distinct optima were identified for two specific objectives: maximizing polysaccharide yield and maximizing delignification. In the low severity regime, the predicted optimum for maximizing polysaccharide retention yielded a 73.3% pulp yield (96.9% cellulose and 92.2% xylan retention), while the delignification focused optimum achieved 83.1% lignin removal. In the high severity regime, maximizing polysaccharide yield resulted in 88.2% cellulose and 67.6% xylan retention, whereas delignification objective achieved 91.3% lignin removal. Chemical and morphological analyses confirmed that varying severity regimes and objectives produce pulps with distinct structural chemotypes. This study establishes a robust sequential RSM model that serves as a powerful tool for precisely tailoring non-wood feedstock fractionation, enabling biorefineries to switch between high yield intermediate pulps and high-purity cellulose streams based on specific market requirements.