In this study, the 2D porous graphitic carbon nitride (g-C₃N₄) nanosheets were successfully fabricated via a facile thermal decomposition polymerization method without any help of templates, and then novel porous g-C₃N₄/CdS complex catalysts of different mass fractions were is situ synthesized by a simple solvothermal process. The results of photocatalytic experiments demonstrate that the coupling g-C₃N₄/CdS cocatalysts exhibit significant enhanced visible-light-driven photocatalytic activity for the decolorization of methyl orange (MO) compared with individual porous g-C₃N₄ and CdS. In particular, an optimal porous g-C₃N₄ content in the hybridized composite has been determined to be 70 wt.%, corresponding to pseudo-first-order rate constant of 0.046 min, which is 7 and 11 times faster than that of pure porous g-C₃N₄ and CdS, respectively. Photoluminescence (PL) spectroscopy measurements clearly confirmed that the recombination of photoproduced electrons and holes in g-C₃N₄/CdS composites was efficiently inhibited due to the formation of heterojunctions. Furthermore, the possible mechanism of enhanced photocatalytic activity and photostability of prous g-C₃N₄/CdS are also tentatively proposed.