It is widely recognized that natural state cellulose consists of both less-ordered and highly-arranged crystalline regions in their molecular structure, and wide-angle X-ray scattering (WAXS) analysis was conducted to determine the crystalline index of native cellulose and optimized nanocellulose. XRD studies were performed to evaluate the crystallinity behaviors of native cellulose and yielded nanocellulose specimens. As shown in Figure 2, the XRD diffractogram profiles for all samples exhibited a similar pattern, which represented the typical semi-crystalline materials with a crystalline peak and non-crystalline broad halo. In addition, all XRD profiles showed the major peaks at around 2θ = 15.1 (1–10), 16.5 (110), 22.5 (200), and 34.6° (004), which indicated the presence of cellulose I structure . From the X-ray curves, it was clearly observed that the XRD patterns of both nanocellulose samples and commercial MCC were similar. This observation suggested that the crystalline structure of cellulose I of MCC had been well maintained after the hydrolysis process to different extents.