A metal-insulator-metal waveguide with an arc-shaped resonator is designed, and the transmission properties are numerically investigated by the finite-difference time-domain method. The results show that the transmission peaks in the transmission spectra result from the resonance of the surface plasmon polaritons in the arc-shaped resonator. The effects of the structural parameters of the arc-shape resonator on the transmission properties are also studied. In addition, this structure can also act as a splitter and achieve a dual function of filter and splitter for subwavelength waveguide.