A metal-dielectric-metal waveguide structure comprising a semi-circular resonant cavity, baffle, and straight waveguide based on surface plasmon polaritons is proposed. When the incident light wave entered the waveguide structure, the semi-circular resonant cavity and metal baffle formed two narrow discrete states and a wide continuous state, respectively. Consequently, the interference effect was observed, which can form two sharp asymmetric resonance spectra, that is, two modes of Fano resonance. To conduct numerical simulation analysis on the transmission spectrum characteristics of the structure, the coupled-mode theory and finite element analysis method were used. Moreover, the effects of structural and medium refractive index parameters on the transmission quality factor and sensitivity characteristics were elucidated. By analyzing the optimization of the structural parameters, the system performance can be flexibly adjusted and optimized by modifying the structural parameters. Furthermore, the transmission quality factors in the two modes are 3.05×10 ⁵ and 4.59×10 ⁵, and their corresponding sensitivities are 800 nm/RIU and 1160 nm/RIU, espectively. The proposed flexible dual Fano resonance structure has certain application values in the study of nanobiosensors, nonlinear optics, and slow light.