This work presents a refractive index sensor based on Bloch surface waves (BSW) with high sensitivity and quality factor (Q). The sensor utilizes a one-dimensional photonic crystal TiO2/MgF2 as a distributed Bragg reflector and employs a LiNbO3 thin film as the top defect layer to excite BSW through a Kretschmann prism. Numerical simulations using the rigorous coupled wave analysis method are conducted to explore various prism configurations, revealing that low refractive index prisms yield superior performance for BSW sensors. The designed sensor achieves a sensitivity of 1600 nm/RIU (or 938 °/RIU) and is analyzed for its full-width at half-maximum and quality factor (Q), with the sensor’s Q value reaching 8000 /RIU (or 13595 /RIU). Through manufacturing error analysis, it was found that the designed sensor has good mechanical robustness, is easy to manufacture, and is also easy to integrate. The results show that the LiNbO3 nonlinear tunable material has great application prospects in the field of refractive index sensors.