Abstract: In order to solve the problem of simultaneous filtering in the multi-channels of wavelength division multiplexing(WDM) system, the design and research of modulation scheme caused by the defects of a hetero-structure photonic crystal multi-channel filter were proposed. From the numerical simulation results, it was shown that the multi-mode filtering property of ring cavity could be overcome and the single wavelength selection and filtering for one channel could be obtained by introducing the point defect in the photonic crystal ring cavity filtering channel. The output resonant wavelength of this filter could be adjusted by changing the refractive index of the point defect of each channel, and the tunable filtering function of each channel was independent. The output resonant wavelength would shift towards the longer wavelength direction when the refractive index of point defect increased. The hetero-structure photonic crystal designing method could provide some theoretical references to realize filtering function for the multi-channel filtering in WDM system.