An eight-channel drop filter based on two-dimensional photonic crystal is proposed. A five-cascaded stub is used to receive 100% reflection feedback. The geometric parameters on the transmission spectra of the bus waveguide output port are investigated. The Fabry–Perot fibre grating theory is used to explain the influences. On the basis of the 100% reflector, a channel drop filter is designed according to the wavelength spacing in the coarse wavelength division multiplexing system. Numerical simulations demonstrate that each channel exhibits over 93% transfer efficiency.