A plasmonic structure consisting of a metal-insulator-metal waveguide, a rectangular cavity and a semi-circular cavity was proposed to investigate the transmission properties by the finite-element method. Simulation results show that there is a sharp and asymmetric Fano profile in transmission spectrum, which is due to the interaction of the local discrete state and the continuous spectrum caused by the rectangular cavity and the semi-circular cavity, respectively. After changing the parameters of cavities, it was found that this Fano resonance position exhibits dependence on the parameters of the rectangular cavity, while is not sensitive to the tiny movement between the two resonators. Meanwhile, the propagation properties of two derivative structures were also studied by changing the mix of two resonators, and the transmission spectrums of these structures can exhibit a sharp and asymmetric Fano profile. In addition, the application of these structures in sensors was also studied by filled the cavities with different refractive index materials, the maximum sensitivity value of which is up to 750 nm/RIU. These studies will provide some theoretical basis for the future high sensitive microchip sensor based on surface plasmon polaritons waveguide.