With the rapid evolution of sensor technology, biomaterials, and micro/nano manufacturing techniques, the performance requirements for flexible electronic devices have been increasingly elevated. These devices not only need to exhibit exceptional flexibility and stability but also require a high level of biocompatibility to adapt to a variety of application scenarios ranging from attachment to the skin surface to implantation inside the body, ultimately facilitating the monitoring and feedback of internal human body information. In this study, by doping Ni particles in Liquid metal (Ni-GaIn) to regulate the surface tension and fabricating them with a biocompatible hydrogel (SA-doped PAAM), an implantable strain sensor was successfully developed. This method not only significantly improves the processability and moldability of liquid metal by reducing its surface tension but also endows the device with excellent stretchability through the construction of a stable hydrogel-liquid metal interface. The device possesses high stretchability and can serve as an implantable stress sensor, stably sensing motion information such as bending angles within biological tissues. This research provides new insights for the design and fabrication of implantable bioelectronics and holds promising application prospects in the field of biomedical engineering.