Simulation on transmittance for different submicron-structures by finite difference time domain method is studied. The objectives of this study are to discuss transmittance for different submicron-structures. Different structures have different effects of transmittance and reflectance; therefore different sizes, shapes, periods and aspect ratios of submicron-structures are discussed in the current study. High transmittance at the visible waveband and heat insulation at the infrared range are expected for application of car window. The simulation results for flat surface and pyramid structures show that the transmittance increases from 95.7 % to 99.8 % at the wavelength of 760 nm and slightly from 96.0 % to 96.3 % at the infrared range. Though the effect of heat insulation slightly decreases while the infrared passes through the submicron-structures, the high visibility helps for car driving safety. The pyramid structure shows the optimal condition for the application of car window at the aspect ratio of 1 to 2 than other shapes.