A novel photonic crystal based hexagonal ring resonator (HRR) based 5-channel DWDM demultiplexer, its design and analysis is reported. The wavelength controlling of each channel is achieved by fine tuning of radius of special hole of HRR. Each channel of DWDM demultiplexer is designed with a PC-HRR consists of a special hole, which is incorporated in between hexagonal contour and input waveguide. And the radius of the special hole of each HRR varies from 95 to 115 nm with a variation of 5 nm. These five different HRR are connected serially by input-waveguide, which is used to couple the light. The air-holes on a silicon slab configuration is used in the device design. The resolved wavelength of this filter is in 1535–1539 nm range, where Erbium-Doped-Amplifier can be used. An average channel coupling-efficiency is 72.4% and channel cross talk is -18.31 dB reported. Photonic band gap of the device is computed by Plane-Wave-Expansion method. EM field analysis of this device is carried out by Finite-Difference-Time-Domain method.