Abstract: In this study, Iraqi bentonite Kara Tepe was used as reinforcing phase in Polystyrene (PS) matrix to form composites. Bentonite clay was prepared as a powder for particles size <45 and <75 μm, followed by calcinations process at 450°C for 2 h. PVA solution used as a coated layer covered the bentonite applied as a filler. Reinforced bentonite powder were added to PS solution at certain quantities. The optical study showed good transmittance value of PS, inter VIS and NIR region but it decreases with the increasing particles size of reinforced bentonite additive. The values of allowed and forbidden indirect transition optical energy gap decrease with the increasing particles size of reinforced bentonite additive up to (2.6, 2.38, 2 eV) and (2, 1.8, 1.30 eV), respectively which it is possible to apply in transistor, capacitors, solar cells, electrical equipment, etc. Optical constants such as refractive index, extinction coefficient, real and imaginary part of dielectric constant of polymer reinforcement bentonite were done. we discovered that these constants are influenced by the bentonite additive ratio and particle size.