A metal-insulator-metal asymmetric structure filter is proposed based on the aperture coupled method, which is composed of two semi-circular cavities, a waveguide and two rectangular apertures connecting the semi-circular cavities and the waveguide. The finite element method is used to simulate and calculate its magnetic field distribution, transmission spectra, bandwidth and edge steepness distribution curves. The results show that the obvious red shift or blue shift phenomenon will be occurred in the transmission curve when the structure parameters are adjusted, and the transmission curve is very smooth. Its pass-band’s transmittance can reach 0.95, its stop-band has the flat characteristics and the transmittance is as low as 0.001. Besides, its pass-band and stop-band all have a wide bandwidth. After optimizing the structure parameters, the filter can realize a similar function of the rectangular filter and the filtering function of channel selection of the three optical communication windows at telecommunication regime. The proposed filter can be well applied in the micro / nano optical integrated devices, especially in optical communication systems.