Compared with the traditional Lorentz line shape, the Fano resonance spectrum with asymmetric line shape has higher spectral resolution and is especially suitable for sensing applications. In this paper, two air holes are introduced in the coupling region of the silicon-based bus waveguide and the runway micro-ring cavity to make the continuous spectrum produce abrupt phase shift, and coupled with the runway micro-ring resonator to form Fano resonance, and in each of the wider spectrum range. All resonance peaks appear as asymmetrical lines. By optimizing the coupling distance and the offset between the air hole and the center of the coupling region through simulation, a silicon-based Fano resonant device with a maximum spectral resolution of 312. 05 dB/ nm and an extinction ratio of 53. 09 dB is obtained. Under the condition that the refractive index change range of the simulated liquid is 1. 33~ 1. 332, the simulation shows that the refractive index sensing sensitivity is 125 nm/ RIU. The simulation results show that the device proposed in this paper has simple structure, compact size and small manufacturing error, which provides a new idea for the application of silicon photonic devices to highly sensitive integrated biochemical sensors.