The optical transmission characteristics and the photonic band gap (PBG) of the nano-film are studied which consists of silica colloidal microspheres with different sizes. Nano-colloid crystal film is self-assembled with light transmitted colloidal SiO2 microspheres on glass substrate. Bragg law is used to analyze the influence of the microspheres size on photonic band gap. In order to achieve omni-directional antireflection in the range of visible light, it is proposed to move the bandgap of colloidal crystals to the ultraviolet (UV) band by changing the size of colloidal particle. It is found that close to 0.5% average reflection can be achieved when the particle size is 112 nm, and duty ratio is 0.45. Experimental results show that the average reflectance of glass surfaces is reduced from 4.3% down to 0.7% in the wavelength range from 400 nm to 800 nm. Through controlling colloidal particle size to move the photonic bandgap position, optimizing crystal structure parameters, the antireflection in visible light band is achieved, and the utilization of visible light by the optical components is effectively improved.