Abstract: Organic modified montmorillonite (OMMT) was prepared by intercalation modification of montmorillonite with Gemini surfactant. The OMMT/polystyrene (PS) composites were fabricated through solution mixing. The OMMT/PS composites and polyethylene (PE) were melt-blended to obtain OMMT/PS-PE composites. The effect of OMMT on the mechanical properties and phase morphology of OMMT/PS-PE composite was analyzed. The characterizations of OMMT by FTIR, XRD and TG show that Gemini surfactant is successfully intercalated into the layer of montmorillonite. The morphological structure of OMMT/PS-PE composites and the changes of the particle size of PS dispersed phase, as well as the relationship between the phase morphology and the mechanical properties were examined by SEM observation and electronic universal testing machine. The results demonstrate that the particle size of the disperse phase gradually decreases with the addition of OMMT. The phase morphology of the OMMT/PS-PE composites changes from "sea-island" to co-continuous structure when the content of OMMT reaches to 2.5wt%. Compared with PE-PS matrix without OMMT, the flexural modulus and elongation at break of OMMT/PS-PE composites are significantly improved, and increases more than about 18% and 50 times, respectively.