We propose an ultra-wide detection range refractive index sensor based on surface plasmon resonance (SPR) with photonic crystal fiber (PCF). The analyte is injected into the central air hole of fiber core. The properties of refractive index sensing are investigated. Simulation results show that the proposed sensor has an ultra-wide detection range from 1.29 to 1.49. The refractive index wavelength sensitivities of x-polarized and y-polarized core mode are -4156.82 nm/RIU and -3703.64 nm/RIU respectively, and the linear fitting degrees are 0.99598 and 0.99236, respectively. The maximum x-pol amplitude sensitivity is -456.589RIU-1 . The maximum y-pol amplitude sensitivity is -1056.33RIU-1 . The designed refractive index sensor has a great potential in the fields of biology, chemistry, environment and medicine.