In conclusion, we have shown an improved XRD method forbetter quantification of cellulose CrI. The method utilizes a sim-ple 3-parameter background model obtained from a representativecrystalline sample and extension of the 2 angle to 75◦. This newmethod uses three distinct amorphous peaks identified from rep-resentative amorphous samples to calculate CrI instead of usingonly one representative amorphous peak. This method enables amore reliable measurement of CrI of cellulose Ias well as d-spacingand crystallite size of cellulose crystallites, offering a useful tool toinvestigate plant cellulose crystallite structural changes during var-ious biological and chemical treatments. The new background andamorphous peaks treatment procedures developed in this studymay also be applied to different cellulose polymorphs to improvethe quantification of CrI.