A surface plasmon resonance based photonic crystal fiber (SPR-PCF) refractive index sensor with high sensitivity and wide refractive index measurement interval is proposed. Using surface plasmon resonance technology to measure the change of resonance wavelength through the fundamental mode loss spectrum to achieve the purpose of measuring different refractive indices of the substance to be tested. The main purpose is to arrange the air holes inside the fiber into a hexagonal shape, and cover the gold layer on the outer side of the fiber, and contact the circular material channel to be tested. It not only helps to accelerate the surface plasma reaction, but also has a simple structure and is easy to measure. The wavelength range of its operation can be adjusted. The simulation results of COMSOL show that the refractive index measurement interval is 1.31~1.38, and the maximum spectral sensitivity of 10000nm/RIU can be obtained. The resolution is 200RIU-1, and the refractive index accuracy is 2.94×10-5RIU.