Abstract: PEO-PDMS based composite polymer electrolytes were prepared by introducing sodium montmorillonite or organic montmorillonite into the polymer electrolyte system, using the solution-cast technique. The adding of a proper content of montmorillonite reduced the crystallinity of the polymer electrolyte, which is benefit for the ionic conductivity. The ionic conductivity of the sample Na-MMT-6% reached 2.24×10^-5 S/cm at room temperature. Meanwhile, the increasing of montmorillonite content also profits the thermal stability and mechanical property. In addition, there exist differences on the performance of polymer electrolyte while adding Na-MMT or OMMT as the same content, because the layer distance of OMMT is larger than that of Na-MMT.