Porous graphitic carbon nitride (g-CN) was prepared by dicyandiamide and urea via the pyrolysis method, which possessed enhanced visible-light-driven photocatalytic performance. Its surface area was increased from 17.12 to 48.00 m/g. The porous structure not only enhanced the light capture capacity, but also accelerated the mass transfer ability. The Di (Dicyandiamide)/Ur (Urea) composite possessed better photocatalytic activity for Rhodamine B in visible light than that of g-CN. Moreover, the Di/Ur-4:5 composite showed the best photoactivity, which was almost 5.8 times that of g-CN. The enhanced photocatalytic activity showed that holes and superoxide radical played a key role in the process of photodegradation, which was ascribed to the enhanced separation of photogenerated carriers. The efficient separation of photogenerated electron-hole pairs may be owing to the higher surface area, O dopant, and pore volumes, which can not only improve the trapping opportunities of charge carriers but also the retarded charge carrier recombination. Therefore, it is expected that the composite would be a promising candidate material for organic pollutant degradation.