A new polymeric gel electrolyte system consisting of poly(ethylene oxide)-modified polymethacrylate (PEO–PMA) with organic ionic liquid dissolving magnesium salt, Mg[(CF3SO2)2N]2, has been developed. The ionic conductance and electrochemical properties of the gel films were investigated. The obtained gel film was self-standing, transparent and flexible with sufficient mechanical strength. Thermal analysis of the gel film showed that it is homogeneous and amorphous over a wide temperature range. The highest conductivity, ca. 3.5mScm−1 at 60°C, was obtained for the polymeric gel containing 80wt.% of the liquid component that consists of 80mol% of EMITFSI (1-ethyl-3-methylimidazolium bis(trofluoromethylsulfonyl)imide) and 20mol% of Mg[(CF3SO2)2N]2. The sort of the ionic liquid affected much on the ionic conductivity of the gel. The dc polarization of a Pt/polymeric gel electrolyte/Mg cell proved that the magnesium ion (Mg2+) can mobile in the present polymeric gel system.