Carbon nitrides (CN) were modified with acid anhydrides to improve the separation efficiency of the electron hole and pyromellitic dianhydride (PMDA), was screened as the most suitable groups introduced into the CN. The factors including preparation condition factors, the degree of the CN polymerization and degradation condition factors were researched. The X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and the infrared spectra (IR) show the structural changes and confirm the successful introduction of PMDA to the bulk CN. The optical properties of modified photocatalyst are investigated by UV-vis diffused reflection spectra (UV-vis DRS) and photoluminescence (PL) spectra and the adsorption performance is detected by the Brunauer-Emmett-Teller (BET). Moreover, the concentration of the main active species center dot O-2(-) increased evidently after the modification during the degradation process. Compared with CN, the photocatalytic degradation efficiency of PCN-290 is about 2 times of that under visible irradiation (lambda > 400 nm).