2D organic g-C3N4 photocatalysts are low cost materials with facile fabrication, suitable bandgap, tunable functionalization, excellent thermal/chemical-physical stability and exceptional photocatalytic behavior, raising considerable interest in photocatalytic and redox research areas. The photocatalytic performance of g-C3N4 mostly relies on the separation/transfer of photo-generated carriers. The mobility properties of the carrier largely determine the formation of reactive species, which have a high impact on surface reactions in the photocatalytic systems based on g-C3N4. This review paper outlines the works carried out so far on the optimization of the carrier mobility dynamics of 2D g-C3N4 materials via the internal and external modification strategies. The peculiar layered planar structure of g-C3N4 allows charge carrier mobility at the interface, in-plane and interlayer, and mechanisms of the charge separation/transfer will also be discussed. Comprehensive conclusions and perspectives on the modification of g-C3N4 leading to satisfactory carrier mobility will be given as well.