The photonic crystal fiber-based surface plasmon resonance (SPR) refractive index sensor is demonstrated by using post-processing technique of photonic crystal fiber (PCF). The coupling of PCF mode field and SPR can be controlled by the air holes collapsing in PCF. The effects of metal film thickness and air hole diameter on the sensor at different wavelength are simulated by using finite element method. The simulation results are analyzed by using the modes matching theory. The amplitude based and spectrum based detection methods are discussed respectively. Refractive index sensitivity 1 700 nm/per refractive index unit (RIU) can be achieved for an aqueous analyte.