Eco-Friendly, non-toxic and biodegradable natural biopolymer electrolyte, Gellan Gum with Magnesium Chloride has been prepared by solution casting technique. The prepared biopolymer electrolyte has been characterized by XRD, FTIR, DSC and AC impedance analysis techniques. XRD study is used to analyze amorphous nature/crystalline nature of the polymer electrolyte. Complex formation between Gellan Gum and magnesium chloride salt has been studied by FTIR technique. The glass transition temperature (Tg) of the polymer electrolytes are obtained by DSC measurement. The highest ionic conductivity 2.91×10− 2 Scm− 1 has been obtained for electrolyte of 1.0 g Gellan Gum with 0.5 M.wt% MgCl2 from AC impedance analysis at room temperature. Transference number 0.97 has been obtained by Wagner’s polarization method for high conducting sample. The Mg2+ cationic transport number 0.35 has been found by Evan’s method for high conducting sample. Magnesium ion conducting battery has been constructed using the high conducting polymer electrolyte. Its open circuit voltage 2.39 V and the battery discharge characteristics are studied.