Hollow silica nanospheres (HSNs) have been widely used as the antireflection coatings due to their low refractive index. However, it is difficult to incorporate them into optical polymer matrices to enhance the visible transmittance obviously using a simple blending method. Rayleigh scattering caused by their larger particle size and agglomerations problem would make the haze and transparency of optical polymer worse. Herein, ultra-small HSNs with the diameter of about 20 nm were synthesized by a reverse microemulsion method. The scale-up preparation was achieved by the high-gravity technology in a rotating-packed-bed reactor (RPB), and then a transparent polyvinyl alcohol (PVA)/HSNs nanocomposite was fabricated via a simple solution blending method. HSNs have an inner cavity size of about 8 nm and the refractive index is 1.342. They can be monodispersed in water and organic solvents respectively by using the different surface modifiers. The prepared PVA/HSNs nanocomposite has a super-high transparency and a low haze, resulting from that HSNs are homogeneously dispersed in PVA matrix without any aggregations, which has great application prospects in optical materials and devices.