An interventional fiber optic strategy, as a representative optical medical technology, is flexible, highly sensitive, minimally invasive, and anti-electromagnetic and has good biosafety. Fiber optics can approach deep cancer lesions and provide direct theranostics, which other optical technologies cannot achieve. However, the realization of cancer sensing and therapy relies on the functionalization of optical fibers, which requires the strict selection and optimization of functional materials used to modify the optical fibers, ensuring high photothermal conversion efficiency without affecting fluorescence detection efficiency. Herein, we propose the use of black phosphorus, which does not interfere with fluorescence and provides a safer and more efficient photothermal effect compared to other nanomaterials, such as graphene, graphene oxide, carbon nanotubes, and MXene. We developed a fiber-optic theranostic probe that combines nitroreductase (NTR) fluorescent molecules and a black phosphorus/gold nanostar (BP/AuNS) nanomaterial hydrogel to develop an integrated strategy for cancer sensing and photothermal therapy (PTT). The sensor has high sensitivity, and the limit of detection (LOD) is 1.61 ng mL-1. BP/AuNS fibers have excellent photothermal effects, and the probe temperature reached 212°C in air as 150 mW of pump power was delivered. In the phantom test, the simulation and test results showed that the fiber probe conferred hyperthermia (>45°C) to an area with a radius of 2.5 mm. These results indicate that the minimally invasive BP/AuNS fiber exhibits excellent sensing performance and high photothermal efficiency, making it promising for tumor diagnosis and treatment and potentially advancing the development of optical fiber medicine.