Tailoring defective conjugated heterocyclic network to make for broaden light absorption and efficient charge separation for photocatalytic application is an urgent assignment for graphitic carbon nitride (g-C3N4) materials. Here we report a ficile “one-pot” solvothermal method to synthesize controllable O-doped g-C3N4 catalysts at low temperature. By this template-free approach, hollow microsphere O-doped g-C3N4 products were obtained. Structure characterization reveals that the as-prepared sample has incomplete heptazine heterocyclic ring structure, and appears O doping in the lattice, which may derived from the activated O2 molecular. With the extending condensation time, the increased heteroelement doping content and narrowed band gap promote the light harvesting and charge separation efficiency. Compared to pristine g-C3N4 prepared under high-temperature calcination, this novel material show remarkably photocatalytic activity for environment pollutant purification and splitting water for H2 evolution, even though the conduction level decrease. This work highlights that the architecture and electronic properties of g-C3N4 based materials could be facile control through mild solvothermal route, which is a reference way for design and fabricate highly efficient non-metal photocatalyst with peculiar feature.