We propose a surface plasmon resonance (SPR) refractive index (RI) sensor based on a novel D-shaped photonic crystal fiber. We used an open air hole coated with gold film to improve SPR effect. The effects of structural parameters on resonance spectrum were analyzed by finite element method (FEM). Three SPR peaks were obtained in the wavelength range of 800nm-1300nm. The simulation results show that the refractive index detection range of the sensor is 1.26-1.38. The maximum sensitivity is 5626.86 nm/RIU and the maximum resolution is 1.78×10-5 RIU at the refractive index of 1.38. The sensor uses photonic crystal fiber with the same air holes diameter. Compared with other D-shaped structures, our sensor can measure larger RI ranges of the analyte.