Acid enhanced ionic liquid (IL) 1-n-butyl-3-methylimidazolium chloride ([C<SUB>4</SUB>mim]Cl) pretreatment has shown great potential for boosting the yield of sugars from biomass cost-effectively and environmental-friendly. Pretreatment with shorter processing time will promote the commercial viability. In this work, pretreatment of reduced Amberlyst catalysis time of 34min was demonstrated to be the most effective among time-varying pretreatments, evidenced by partial removal of hemicellulose and cellulose crystal transformation of Arundo donax Linn. A higher fermentable sugar concentration of 10.42g/L (2% substrate) was obtained after 72h of saccharification than the others. Total processing time to reach 92% glucose yield was cut down to approximately 26h. Progressive deconstruction of crop cell wall was occurred with increased catalysis time by gradual releasing of H<SUB>3</SUB>O<SUP>+</SUP> of Amberlyst. However, vast lignin re-deposited polymers on fibers could hinder further enzymatic hydrolysis. These discoveries provide new insights into a more economic pretreatment for bioethanol production.