The means of homogenization method and finite element method was deduced to predict the effective properties of nano-modified plastics. Steps of simulation were given. The effective properties of EVA/TiO2 nanocomposites were studied by the content and the shape of nanoparticles. The results of the prediction and the test were close basically. It was showed that the method of predicting the effective properties of nano-modified plastics by means of homogenization method and finite element method was feasible and the effects of actual microstructures of materials could be investigated too.