A photonic-crystal fiber (PCF) based on the surface plasmon resonance (SPR) effect with low confinement loss and high sensitivity response is designed and its optical properties analyzed when varying different parameters. The SPR-based PCF design is analyzed to enable control over its light propagation and evanescent properties. In this investigation, gold (Au) is used as a plasmonic material to generate the SPR effect at the interface. The simulation results reveal a maximum sensitivity response of 45,303 nm/RIU with resolution of 7.0634 × 10^–6 and low confinement loss of 0.575 dB/cm in the wavelength range from 1.2 to 2 µm. A high figure of merit of 378 with low full-width at half-maxima is also obtained. The proposed structure thus offers ultralow confinement loss and high sensitivity.