Cellulose nanocrystals (CNCs), a unique and promising natural material extracted from native cellulose, have attracted considerable attention owing to their physical properties and special surface chemistry. This review focuses on chemical conjugation strategies that can be used for preparation of fluorescent-molecule labeled CNCs and the development of biomaterials.Furthermore, their application in the detection of metal ions and future development prospects are discussed. We hope to provide a clear view of the strategies for surface fluorescent modification of CNCs and their application in detection of metal ions.