Abstract: In order to detect the refractive index of surface plasmon resonance (SPR) with high sensitivity, a SPR sensing structure based on single core photonic crystal fiber with large core was proposed. The full vector finite element method was used to simulate and analyze its sensing characteristics. The results show that the structure has a wide range of refractive index sensing range (1.36~1.55). At the same time, the structure has high sensing sensitivity and the average sensitivity is 12139nm/RIU. With refractive index of 1.36~1.42, the linear sensor sensitivity is 5646.4nm/RIU and linearity is 0.9317. With refractive index of 1.42~1.57, the linear sensor sensitivity is 15326.8nm/RIU and linearity is 0.98738. Sensing characteristics appear in obvious linear subsections. The results provide an important theoretical basis for the realization of high sensitive photonic crystal fiber SPR sensors.