Polymer (PVdF-CO-HFP) composites containing nanoMgO filler and lithiumtriflate saltwere prepared using a solution cast technique. All samples were characterized using different techniques such as X-ray diffraction (XRD), thermal analysis (TG, DSC), Fourier transform infra–red spectroscopy (FT-IR) and scanning electron microscopy (SEM). Structural investigation of all samples were conducted in a well – sequence; firstly, in presence of nano filler, and secondly in presence of LTF salt to study the structural changes (crystallinity), and their effects onmelting, morphology and thermal stability behavior. In presence of definite filler and salt concentrations, the basic polymer matrix exhibited suitable structure, followed by good conduction properties. A sample containing 6wt% MgO and 25 wt% LTF showed AC-ionic conductivity value of about 8.78 × 10−5 ohm−1·cm−1 at roomtemperature. The same sample exhibited good thermal stability behavior (Td=402.99 °C). To further investigate the stability of this sample, electrochemical and mechanical stability properties were also studied.