In this paper, we propose and numerically characterize the optical characteristics of a high-sensitivity dual-polarization four-channel surface plasmon resonance (SPR) refractive index sensor with wide detection range and high linearity based on photonic crystal fiber (PCF). Four light transmission channels are constructed by using big air holes. The small rectangular air hole in the center of the fiber core is used to add asymmetry. We use gold plasma material to achieve better sensing performance. A thin film of TiO2 is placed on the PCF surface, which assists gold in the adhesion on PCF. The maximum wavelength sensitivity of the sensor can reach 20 000 nm/RIU in both x and y polarization modes. While the maximum wavelength resolution of the sensor is 5×10-6 RIU. The average wavelength sensitivity reached 15 900 nm/RIU and 15 800 nm/RIU in x and y polarization modes. The sensor features R2=0.996 9/R2=0.996 6 high linear performance in x and y polarization modes and the maximum figure of merit (FOM) values of 509.13 RIU-1/489.63 RIU-1 in x and y polarization modes. Besides, the sensor’s detection range is 1.26–1.36, which is a wide refractive index detection range.