In the present work, thermal and mechanical properties of nanocomposites PP+ZrO2 are studied. The presence of zirconium dioxide in PP increases its thermal stability and mechanical properties of nanocomposites. The AFM studies show that a change in upper molecular structure of polypropylene as well as a chipping of structure elements of surface morphology occur with addition the nanosize powder to the polymeric matrix. The thermal stability and mechanical properties generally increases with increasing amount of zirconium dioxide. Improvement in thermal stability of PP occurs by the addition of 5% ZrO2. It was experimentally shown that increasing of volume content of ZrO2 changes the mechanical durability of nanocomposite PP+ZrO2 with extremum, i.e. the concentration of ZrO2 up to 5% increase durability, and more than 5% decrease it. These results prove that ZrO2 nanoparticles with concentration up to 5% are the centers of structure nucleation, and further increasing of nanoparticles concentration leads to destroying of physical structure of polypropylene.