Heating press films of alloy of polystyrene with poly (styrene-butadiene) rubber were measured by the thermally stimulated current and small-angle X-ray scattering and the compatibility on alloy was discussed. Small-angle X-ray scattcring was interpreted in terms of the Porod Law which leads to values for interface layer thickness (compatibillity zone). The relation with compositions of alloy was discovered. A correlation distance and invariant Q were calculated by Debye-Bueche theory. A cormlation distance represents the mean-square electron density fluctuation and thermogeneity of alloy was analyzed using invariant Q. Solvent-cast films of alloy were measured by transmission electron microscopy

and the phase distribution of alloy was investigated.