Abstract: A photonic crystal fiber refractive index (RI) sensor based on enhanced surface plasmon resonance (SPR) effect is proposed. The sensor structure is spliced with a photonic crystal fiber (PCF) by a fiber fusion splicer, so that an air hole is introduced in the middle of the photonic crystal fiber to form a PCF-air hole-PCF optical fiber sensing structure. Then, a thin gold film is deposited on its surface by using magnetron sputtering coating process. Experiments are carried out to investigate the response of the refractive index and temperature of the sensor. The results show that in the refractive index (RI) range of 1.333−1.389, the sensor has an average RI sensitivity of 2 142.52 nm, with a linearity of 0.981 and a quality factor about 13.10. Experimental results show that the sensor is not sensitive to temperature. Compared with the PCF sensing structure without air hole, the air hole introduced enhances the SPR effect, so that the sensor has a good resonance peak depth. Benefiting from the above advantages, this type of sensor is expected to be applied in fields such as biomedicine and environmental monitoring.