Polymer nanocomposite materials caused attention because of the properties of the pure material properties can be extremely improved by adding a nano-sized fillers. This paper consists of two parts. The first one is theoretical part and it is about nanocomposites and fillers (such as carbon nanotubes, montmorillonite, silica) their structure and application. The experimental part of this paper is about novel designed polymer composite samples with different filler percentage composition, using Polyethylene Oxide as matrix and the fillers – tetraethylorthosilicate and silica nanoparticles as C8H20O4Si, carbon nanotubes, montmorillonite and Lithium perchlorate. A composite polymer solution was prepared by dissolving PEO in ethanol. The effect of nanocomposite’s preparation method's and filler concentrations onto polymer nanocomposites was evaluated by Fourier transform infrared spectroscopy (FTIR), Vickers hardness, tensile strength and electrical conductivity analysis. It was observed, that addition of silica nanoparticles to PEO composite increase Vickers hardness, at the same time addition of Lithium perchlorate decrease Vickers hardness and tensile test Young’s modules. FTIR transmittance results confirm, that all of our SiO2-, TEOS- and MMT-containing nanocomposites are injected amorphous SiO2 nanoparticles. Young’s module increases with MMT, CNT, SiO2 and TEOS fillers addition. Electric conductivity increased with respect to the enhancement of the filler, however excessive amount of these additives caused the conductivity to decrease.