By the incorporation of nanoparticles into a polymer matrix the properties of the nanocomposites can be significantly improved compared to the starting polymer. As the incorporation process appears to be challenging due to possible agglomeration of the nanoparticles it is very important to control it online. In this research, transparent SiO2-polypropylene(PP) nanocomposite was examined with the optical turbidimetric method directly at the extruder. Furthermore, comparative scanning electron microscopy measurements are presented. It is shown that the turbidimetric analysis can be used for online quality control of nanocomposites.