Constructing hydrogels with both remarkable mechanical and self-healing properties is highly desirable for soft electronics, yet remains challenging due to conflicting demands on chemical bonds and polymer chain mobility. Herein, a highly stretchable, self-healing, and conductive gelatin methacryloyl (GelMA) hydrogel is developed by incorporating polyvinyl alcohol, N-(2-amino-2-oxoethyl)-2-propenamide, sodium tetraborate, and sodium chloride into GelMA, followed by a two-step polymerization process. The introduced novel interpenetrating networks, hierarchical hydrogen bonds (weak and strong H-bonds), and borate ester bonds (BEBs) synergistically improve the mechanical strength, and concurrently function as sacrificial bonds for energy dissipation under deformation. Moreover, the constructed reversible BEBs and weak H-bonds enable autonomous self-healing at room temperature. The resulting hydrogel achieves remarkable stretchability (≈160%), tensile strength (≈130 kPa), and self-healing efficiency (86%), surpassing previously reported GelMA hydrogels. Importantly, a self-healing GelMA hydrogel strain sensor is demonstrated, featuring a high gauge factor (≈3.28), ultra-low detection limit (0.1%), and excellent recovery of sensitivity (≈100%) and detection range (≈75%) after damage. Successful monitoring of subtle and large-scale human motions with both original and healed sensors highlights the device's durability and longevity. This study provides a promising approach for the rational design and practical application of GelMA hydrogels in wearable bioelectronics.