Abstract: To address the current challenges of difficult removal and potential residuals of soft tissue foreign bodies, this paper utilizes the principle of different light reflection degrees between foreign bodies and tissues to construct a foreign body localization device based on modified PMMA optical fibers. A light-guiding fiber transmittance method is designed for the localization of soft tissue foreign bodies. To verify the practicality and reliability of the system, tests and comparisons were conducted on biological tissue models. The results show that the device can locate foreign bodies more efficiently and at lower cost, facilitating the complete removal of soft tissue foreign bodies.