Interphase interaction influence on physical and mechanical properties of polymer composites filled with disperse particle is discussed. It is show that fractal size of the filler particles surface is substantially told on the process of interphase layers formation. In frame of fractal description some correlations for prognosticate of interphase layers parameters into polymer composites filled with disperse nano-size particles have been proposed, namely, relative port of polymer phase, which is adsorbed at the surface of filler, and interphase layer thickness. The interrelations between macromechanical characteristics of heterogeneous medium and fractal parameters of interphase layers have also been taken.