In this study, a flexible sensor is successfully fabricated using self‐healing nanocomposite hydrogels for monitoring human movement. The eco‐friendly cellulose nanocrystals (CNCs) are used as nano‐reinforcing materials, and the mechanical properties and self‐healing efficiency of the materials are improved. The self‐healing efficiency of hydrogels are realized by introducing a variety of reversible non‐covalent interactions such as hydrogen bonding, borax chelation, and metal coordination. Notably, the mechanical strength and self‐healing efficiency of these nanocomposite hydrogels can reach 2.8 MPa and 89.9%, respectively. Importantly, these self‐healing nanocomposite hydrogels have been widely used in wearable flexible sensors to achieve high sensitivity to large‐scale human movement. It is of great significance to design functional materials with good biocompatibility, sensitivity, and mechanical strength for wearable sensors.