Abstract: Computer refractive index and transfermatrix theory are used to study the influence of adsorp tion on one - dimensional trip le - sects photonic crystalwith symmetry and transmission peak. The results show that, n reflected wave, the reflectivity of forbid2 den band decreaseswith the increase of extinction coefficient, when k increases to 0. 005, the border of forbidden band is vague and there is no obvious forbidden band, in transmission wave, with the increases of extinction coefficient, the border of forbidden band is gradually vague, when k increases to 0. 003, reflectivity decreases to 0. 35. Photonic crystal extinction coefficient has obvious influence on transmission peak in forbidden band, when k equals to 0. 001, transmission index decreases to 0. 15, with the increase of extinction coefficient, the width of semi - peak of transmission peak increases but there is no influence on central wave length of transmission peak.