We design a T-Shaped wavelength division de-multiplexer in two-dimensional (2D) photonic crystal based on the coupling resonance characteristics. In this structure, three high effective and relative narrow bandwidths optical wavelengths (1 310, 1 440, and 1 550 nm) are obtained by changing the radius of the ring and cavity rods. The method of the finite-difference time-domain is used to investigate the characteristics of the coupling resonance characteristics of the ring and the cavity. The calculation results show that transmission rates of these three wavelengths are all reach up to 95% and achieve with 5-nm mean value of bandwidth.