In this paper, a highly sensitive surface plasmon resonance sensor is proposed on the basis of a miniature tapered single-mode fiber. The sensing area of the tapered fiber is coated with graphene, silver and titanium dioxide layer. The graphene layer is used to increase the light absorption rate, and the titanium dioxide layer is used to protect the silver layer from oxidation and improve the sensor sensitivity due to its high dielectric constant. And optimizing the thickness of graphene, silver and titanium dioxide layer. According to the simulation calculation results, when the graphene is 15 layers, the silver layer is 40 nm, and the titanium dioxide is 20 nm, high-performance SPR can be obtained. The sensor has a detection range of 1.32–1.38, and its sensitivity can reach 8750 nm/RIU when the external refractive index is 1.38. The research results have potential application value for the design of high-performance SPR sensors.