In this paper, we report the successful hydrothermal synthesis of CuGaO2 nanoplates with critically small size and their deposition ways to fabricate effective p-type semiconductive photocathodes in dye-sensitized solar cells (DSCs). Based on an efficient P1 dye and an iodide electrolyte, the optimal CuGaO2 photocathode has achieved remarkably high photocurrent density, up to 2.05 mA cm-2. To the best of our knowledge, it is the highest record achieved by nanocrystalline p-type semiconductors besides NiO. The light harvesting, charge collection in CuGaO2 and NiO based DSCs have been symmetrically compared. Owing to critical size control on CuGaO2 nanoplates and subsequent mechanical press for photocathode film deposition, light harvesting efficiency of CuGaO2 photocathode has been for largely elevated to a comparable level to that of the NiO reference. Another noteworthy feature is the remarkably high charge collection efficiency of CuGaO2 photocathode, which should be benefit from the nature of delafo