In order to improve the spectral sensitivity and simplify the fabrication process, a novel elliptic side-core photonic crystal fiber (PCF) sensor model with high sensitivity based on surface plasmon resonance (SPR) was designed. The air hole of the elliptic side-core photonic crystal fiber consists of a circular hole and three elliptic holes of different sizes. The left elliptic hole is coated with a gold nano film. The sensing characteristics of the sensor were analyzed numerically by the finite element software COMSOL. It is found that the formant of surface plasmon resonance has a high sensitivity to the change of refractive index of the measured liquid, and the sensitivity of the photonic crystal fiber sensor varies with the ellipticity and the thickness of the gold nano film. When the refractive index range of the liquid to be measured is 1.41 ~ 1.44, the maximum sensitivity of the sensor is up to 95000 nm/RIU(RIU is the unit of refractive index). Compared with the existing studies, the sensitivity of this PCF-SPR sensor is 3.7~47.5 times that of the existing typical PCF-SPR sensor in the same refractive index measurement range. The sensitivity is significantly improved and the preparation is simple.