In this paper, the influence of organo-modified montmorillonite (oMMT) on the properties and structure of ultra-high molecular weight polyethylene (UHMWPE) are studied. The technology of preliminary mechanical activation of oMMT in a planetary mill was proposed. The structure and morphology of oMMT before and after mechanical activation in a planetary mill were investigated using scanning electron microscopy and IR spectroscopy. It was found that preliminary mechanical activation leads to dispersion and increase in the porosity of oMMT. Heat treatment at the temperature of the composite material processing does not lead to the destruction of organic modifiers. Studies of the mechanical properties of polymer-silicate composites have revealed that the introduction of preliminary mechanically activated oMMT contributes to the increase of tensile and compressive strength of the composite material based on ultra-high molecular weight polyethylene.