In addition to thermal and acoustic insulation properties of aerogels, their optical properties is one of the main characteristics. Research on optical properties of traarent silica aerogels is mainly focused on materials synthesized by supercritical drying method. However, the amount of research conducted on investigation of light reflectance properties of opaque silica aerogels dried at ambient pressure is scarce. Additionally evaluation of optical properties of aerogel blankets has not yet been carried out. In this work, TEOS based silica aerogel particles and their blankets were synthesized by two-step sol-gel process under ambient pressure. The effect of key parameters on the pore structure, physical and hydrophobic properties of silica aerogel particles were investigated. The light reflectance properties of samples with different pores structure was measured and the relationship between the pores structure and optical properties was discussed. The physical and chemical properties and pores structure of silica aerogels were characterized by nitrogen adsorption-desorption analysis, FE-SEM images, FTIR spectra, contact angle and 3M methods. Reflectance spectrophotometer was used to measure light reflectance properties of silica aerogel particles and blankets. The results point to the fact that the produced silica aerogel particles are superhydrophobic with contact angle of 155 degree and have porosity greater tha 80%, specific surface area of 700-900 m 2 /g , mesoporous structure with 6-22 nm pores and refractive index of about 1.05. The SEM images of aerogel blankets showed that the fiber surface and micro pores of the fibrous matrix were sufficiently coated by the silica aerogel particles. The optical properties of silica aerogel particles and blankets are greatly influenced by the pores structure (pores size and pore size distribution and particles size) and physical properties (porosity, density and refractive index) of silica aerogel particles which in turn are controlled by the synthesis conditions including sol-gel parameters, ageing and surface modification conditions. Also, the weight and thickness of the fibrous layer and the aerogel particles distribution in the blanket structure influenced the optical properties of obtained aerogel blankets. However, the pores structure of aerogel particles played the major role in the traarency or opacity of the blankets. The results showed that high content of catalyst leads to silica aerogel particles with pore diameter of 22 nm. In the presence of insufficient water and catalyst, incomplete hydrolysis and condensation reactions occurred leading to a weak gel network and more shrinkage during drying step. Therefore, the aerogel particles with higher density and less porosity with smaller pores were produced and resulted in much light scattering. Traarency of the aerogel blanket samples synthesized with different molar ratio of the catalysts are similar and higher than the neat fibrous layer. A decrease in the synthesis temperature from 50 to 30 ? C led to particles with xerogel structure, low porosity and high density of 0.53 g/cm 3 . These particles and blankets exhibited higher light scattering and reflectance. Also, surface modification conditions considerably affected the optical properties of silica aerogel particles and blankets. In hydrophilic silica aerogel without surface modification step in synthesis process, the capillary forces were increased during drying step and more shrinkage of gel network led to the structure with smaller pores size and lower porosity and higher density which increased light reflectance in silica aerogel particles and blankets. The effect of sol volume on the optical properties of aerogel blanket samples was also investigated and it was found that due to increase in sol volume, the light reflectance of the blankets decreased and the greater traarency was achieved due to the increase in the amount of aerogel particles in the blanket. The silica aerogel pores structure on the optical properties was more effective for blanket samples synthesized by nonwoven layer with less thickness and weight.