A optical fiber with hole-assisted structure is proposed to construct the surface plasmon resonance (SPR) refractive index sensor. The finite element method is utilized to analyze characteristics of the surface plasmon resonance sensor. The effects of the thickness of metal films, fiber core size, and refractive index of liquid on the resonance wavelength are investigated. The sensitivity of sensor is also given. The result shows that the resonance wavelength is sensitive to the thickness of metal film and refractive index of liquid, while the resonance wavelength doesn't change basically when the fiber core size. The proposed surface plasmon resonance sensor exhibits high sensitivity up to 10-4.