<p>The rapid proliferation of wearable electronics has sparked significant research interest in fabric-based electromechanical sensors for continuous human motion tracking, human-machine interaction, and precision rehabilitation. However, the development of environmentally friendly and durable functional fibers or textiles with superior flexibility for fabric-based electromechanical sensors is challenging. In this study, we developed soft and biodegradable magnetic macrofibers using a stretching-twisting method applied to glycerol-plasticized bacterial cellulose (BC) strips embedded with CoFe₂O₄ magnetic nanoparticles. The resulting magnetic macrofibers demonstrated superior mechanical properties, possessing a tensile strength of 33 MPa with a breaking strain of 3.5% while maintaining sufficient structural integrity to sustain a 2 kg load-bearing capacity. Additionally, the macrofibers were fully biodegradable by cellulase within 15 d, leaving only CoFe₂O₄ nanoparticles that could be adsorbed and recovered by magnets. Furthermore, the fabric-based magnetoelectric sensor constructed by integrating a coil and the magnetic fabric woven by macrofibers demonstrated exceptional electromechanical coupling efficiency across an extended operational range (0.5–10 cm coil-to-textile distance). The superior distance sensitivity, stability, and durability of this sensor enabled real-time monitoring of human motion patterns under dynamic conditions. Therefore, BC-based magnetic macrofibers provide a promising strategy for developing eco-friendly and durable electromechanical sensors for sports training and rehabilitation monitoring.</p>