The vertical deposition self-assembly method is adopted to prepare three dimensional silica colloidal photonic crystals.The optical property of silica colloidal photonic crystals is measured and analyzed by UV- visible- near- infrared spectrophotometer.The results show that the depth of photonic band gap increases and the transmittance reduces as concentration of colloidal silica microspheres increases，but the band gaps central wavelength is consistent with these concentrations.Furthermore，a unique optical property is found and the causes is analyzed when the incident light is along different angles at the top surface of silica colloidal photonic crystals.