g-C3N4 has been widely investigated in photocatalytic water splitting, even though they still suffer low specific surface area and high carrier recombination. Here Co-doped g-C3N4 (Co-C3N4) has been successfully synthesized under an argon atmosphere to 550 degrees C for 4 h via pyrolysis of an organic-inorganic hybrid precursor which was pre-prepared through the hydrothermal procedure. The Co-C3N4 possesses a higher specific surface area of 82 m(2)/g, which is 16.4 times as high as that of the bulk g-C3N4. On the other hand, the in situ Co doping can extend the light absorption region to visible light and greatly improve the charge transfer rate. Both the changes in surface area and optical property are beneficial to the photocatalytic reaction. The Co-C3N4 photocatalyst with the optimal ratio of cyanuric acid to melamine for 1:40 exhibited an excellent H-2 production rate of 741.6 mu mol g(-1) h(-1) under Xe lamp irradiation. The possible formation mechanism of tubular Co-C3N4 is proposed. Meanwhile, designing unique organic-inorganic hybrid structures may open up a new way for excellent photocatalytic water splitting.