<p> Shape reconstruction and force measurement of surgical diagnostic tools are crucial to ensure surgical safety. This study focuses on the strain transfer of an overall flexible fiber Bragg grating (FBG) shape sensor. A theoretical equation of strain transfer was established, with the fiber and bonding layers as the core structures. The response characteristics of the fibers under axial and radial forces were investigated. Through finite element simulations, the strain values of the bonding and fiber layers were analyzed and compared with the theoretical values to determine the influence of the bonding layer thickness, elastic modulus, encapsulation length, and Poisson’s ratio on the strain transfer. A 260-mm-long, 2-mm-diameter, substrate-free FBG shape sensor was encapsulated, and axial/radial force sensing experiments were conducted to verify the theoretical force-wavelength change model. Additionally, shape reconstruction experiments were performed on a flat surface, achieving a 3.68% shape reconstruction accuracy. In surgical diagnosis and treatment, this research enables doctors to monitor the in vivo status of surgical tools and their interactions with tissues in real time, thereby preventing tissue damage, enhancing surgical safety and precision, and laying a theoretical foundation for the quantitative analysis of nociceptive perception in medical endoscopic diagnosis and treatment.</p>