A photonic crystal narrow band filter at green lightwave band is designed with optical transfermatrixmethod, and some factors affected are studied. The results are shown that the centerwavelength can be shifted to 532nm of green lightwave band by selecting suitable parameters of photonic crystal, and the linewidth is equal to 0. 0131nm when N = 9. Moreover, the number of period layers is larger; the spectral line width is narrower. The center wavelength is shifted to shorterwave, and there is no change in line width when thickness of defectmode is thinner. The linewidth is narrowerwhen the incidence angle is larger, and it is almost same between 0°and 3°. This filter at green lightwave band is expected to be applied to blue-green light communication.