Zinc chloride was utilized as the multi-functional modifier with dicyandiamide to synthesize porous g-C3N4, it not only played the role of pore-former in the resulting composite, but also acted as the assistant in succeeding adsorption of methyl orange (MO). Adjusting the quantity of ZnCl2 additive combined with the concentration of acidic washing liquid could control the amount and distribution of residual zinc species in the g-C3N4, in order to enhance the activity of the photocatalyst. The resulting composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis diffuse reflection spectroscopy (UV-vis) and X-ray photoelectron spectroscopy (XPS) as well as photoluminescence (PL) to assess the influence of residual zinc species on the physical and optical property of the composite. And they were evaluated in the photocatalytic degradation of MO in the visible light region, exhibiting an activity 240% higher than that of g-C3N4. (C) 2015 Elsevier Inc. All rights reserved.