This invention discloses a coating method to apply a layer of nano-particles adsorbed on submicron ceramic oxide particles, which can prevent the agglomeration of nano-particles by the effects of Brownian motion and van der Waals force. Using this method, nano-sized titania can be uniformly coated on the surface of silica. This method is conducted in an aqueous solution and able to fabricate a coating layer in a controlled thickness between 5 to tens nm. After calcination, the coated particles can be assembled to form a photonic bandgap crystal. This invention also discloses a coating method to apply a uniform nano TiO2-coating layer on the SiO2 photonic bandgap crystals.