In order to achieve high sensitivity sensing in the near-infrared band, a photonic crystal fiber refractive index sensor based on surface plasmon resonance is designed and investigated in this paper. The air holes in the cross-section of this fiber are arranged in a circular lattice, which show the sunflower shape. The outer surface of the fiber cladding is deposited with a nano-film of indium tin oxide, and the change of refractive index of the surrounding environment is sensed by the coupling of the defect mode and the surface plasmon mode. The optical properties and sensing performance of this sensor are studied in detail by finite element numerical simulations. The results show that the sensor has a large refractive index sensing range and a high sensitivity.The refractive index measurement range is 1.29~1.39, the maximum wavelength sensitivity is 19659 nm/RIU, and the refractive index measurement accuracy is 2.92×10-5 RIU.