Abstract: The graphite phase carbon nitride (g-C3N4) semiconductors with different morphologies and photocatalytic performance were prepared by polycondensation method, using urea and melamine as precursors respectively. The catalytic performance of the g-C3N4 was measured by the reduction of CO2 in methanol under light irradiation. X-ray diffraction (XRD)、Scanning electron microscope (SEM)、Transmission electron microscope (TEM)、UV-vis spectrophotometry (UV-vis)、Fourier transform infrared spectroscopy (FTIR)、Specific surface area measurements (BET) and Fluorescence spectrum (PL) were applied to analyze the influence of different precursors to the photocatalytic activity of g-C3N4. Results showed that g-C3N4 using urea as precursor had better photocatalytic activity for CO2 reduction and the formation rate of methyl formate (MF) in methanol reached up to 512.8μmol/gcat.h, nevertheless that of the g-C3N4 made from melamine was only 257.3 μmol/gcat.h.