A dual core single channel photonic crystal optical fiber surface plasma resonance biosensor based on TiO2 film is proposed to enhance the sensitivity. A layer of TiO2 film is added on the surface of the sensor silver film, which can isolate oxygen to prevent the oxidation of silver and improve the sensitivity of the sensor. The coupling characteristics and performance of the sensor are numerically analyzed based on the full vector finite element method. It is shown that there is a highly linear relationship between the analyte refractive index and the resonant wavelength of the sensor in the sensing range of 1.33-1.38, the adjusted linear correlation value is 0.9806, and the average sensitivity is 4200 nm·RIU -1. In addition, the effects of photonic crystal fiber air hole size, silver film thickness, TiO2 thickness and other parameters on the performance of the sensor are further carried out. The result shows that changing the structure parameters can optimize the output spectrum of the biosensor and improve the sensor performance.