Abstract: The microstructures of two samples of latex dispersion system and the influence of their blending on the crystallization behavior were investigated by means of synchrotron small-angle X-ray scattering(SAXS) technique.The experimental results confirmed that the latex dispersion at a volume fraction of 50% composed of styrene-butylacrylate copolymer did not show up crystalline structures at room temperature.By virtue of fitting the scattering intensity distribution curve,the average radius of the latex particle was 76 nm,which is smaller than the value determined by dynamic light scattering(80 nm).However,the crystalline structure can be probed in the latex dispersion of styrene-butadiene copolymer with a solid content of 50%.Each Bragg peak in the scattering profile can be assigned to one or several crystal indices by assuming diffraction from a face-centered-cubic crystalline structure with a lattice constant of 212 nm.The diffraction peaks can be detected after mixing the two latex dispersion samples,implying that the partial crystallites in the original latex solution are still stable in the blending process.