Plant-based nanocellulose is a class of emerging sustainable nanomaterials derived from natural resources. It not only maintains the sustainable features of plant fibers, but also has unique properties including nano dimensions, high aspect ratios, and high mechanical properties, which enables its use in advanced applications. Based on preparation routes and morphological structures, nanocellulose can be classified into cellulose nanocrystals and cellulose nanofibrils. In this book chapter, different processing routes are evaluated in terms of reaction conditions and efficiency, as well as environmental friendliness. Moreover, the properties of the resultant nanocellulose are compared in terms of chemical composition, morphology, surface charge, crystallinity, thermal stability, etc. Altogether, this chapter provides a comprehensive understanding of the pros and cons of different preparation routes for nanocellulose productions and subsequently gives guidance as to how to best utilize their performance.