In this study, we provide a seed-induced solvothermal method to grow various TiO2 nanostructures on the surfaces of g-C3N4, such as 0D nanoparticles, 1D nanowires 2D nanosheets and 3D mesoporous nanocrystals. We show that the "seeding" endows g-C3N4 with anchoring sites toward the heterogeneous nucleation growth of TiO2, and the distribution of the loaded TiO2 can be controlled by tuning the amount of nucleation in the dispersion. Among synthesized nanostructures, seed-grown Meso-TiO2/g-C3N4 hybrids exhibit the highest photocatalytic activity upon visible light irradiation using methyl orange and phenol as probe organics, which are about 2-4 times and 29-37 times as high as those of direct-grown Meso-TiO2/g-C3N4 without seeding and bare g-C3N4 for degradation of MO and phenol, respectively. The enhancement of photocatalysis can be ascribed to the adequate separation of photogenerated electrons at the heterojunction interfaces and dominant contribution of photoinduced holes mainly caused by the well-constructed nano- architectures.