Diverse cell wall compositions were subjected to pretreatment and saccharification to produce bioethanol from 20 Erianthus arundinaceus accessions. Using four typical pairs of biomass samples, various physical and chemical pretreatments were employed to extract cell wall polymers. Mild chemical pretreatment (2% NaOH and 50 °C) yielded complete biomass saccharification, whereas the liquid hot water pretreatment achieved the highest bioethanol yield with a full sugar-ethanol conversion rate. Notably, the extraction of the lignin p-coumaryl alcohol (H) monomer greatly enhanced biomass saccharification, which may be attributed either to the improved accessibility of cellulose to enzymes after effective removal of lignin or to the maintained native cellulose microfibrils from the relatively less co-extraction of hemicellulose. Hence, the results suggested that the H-monomer-rich lignin may slightly associate with cell wall networks for greatly enhanced lignocellulose enzymatic hydrolysis after mild pretreatments. The present findings provide a strategy for both cost-effective biomass process technology and precise lignocellulose modification for bioenergy.