Cellulose is an abundant renewable polymer resource. Cellulose nanocrystals (CNCs) with high crystallinity can be obtained by hydrolysis with strong acid. After evaporation at a suitable concentration, the suspension of CNCs is dried and self-assembled to form cholesteric liquid crystal film of CNCs. CNCs chiral liquid crystal film exhibits excellent circularly polarized light properties, and is of grant importance in the field of optoelectronic technology. In this review, the liquid crystal behaviors and preparation methods of CNCs are summarized. The structural color properties as well as the pitch regulation of CNCs film by physical and chemical methods are emphatically discussed. At the same time, the circularly polarized light properties of CNCs chiral liquid crystal film are comprehensively introduced. The research progress and application technology of circularly polarized light reflectance properties and circularly polarized luminescence emission performance are summarized and prospected. The difference between the left-handed and right-handed circularly polarized light properties of CNCs chiral liquid crystal film makes it have broad application prospects in liquid crystal displays, optical anti-counterfeiting, sensor devices and other fields. In addition, CNCs film materials with circularly polarized luminescent performance that could be prepared by a variety of methods (such as adding luminescent molecules or metals) can be used as chiral probes to detect excited states, which has potential application values and development space in a series of optical applications.