A polypeptide nanofibers (PNs)-modified optical fiber surface plasmon resonance (SPR) biosensor for specific detecting of rabbit IgG was proposed in this article. Based on the optical properties, biochemical properties, and programmable characteristics of PNs, the proposed SPR biosensor has the advantages of ease preparation, low toxicity, a large surface area, and high bio-sensitivity. In this study, the SPR biosensor was specifically developed to detect rabbit IgG. The bio-sensitivity of 1.36 nm/( $\mu \text{g}$ /mL) and limit of detection (LOD) $0.015 ~\mu \text{g}$ /mL are achieved experimentally. Compared with other single nanomaterial modified SPR biosensors, the developed biosensor has the higher bio-sensitivity and lower LOD. These findings indicate a significant improvement in the performance of PNs-modified biosensors. Furthermore, based on the programmable characteristics, the proposed sensor can be applied in various biosensing environments (such as nucleic acid, biological small molecules, glucose, etc.), providing customized solutions for diverse sensing needs. This significantly expands the potential applications of PNs-modified optical fiber SPR biosensors.