Due to the unique structure of perovskite materials, their capacitance can be improved by introducing oxygen vacancy. In this paper, the LaMnO3- δ material containing oxygen vacancy was synthesized by molten salt method in KNO3 NaNO3 NaNO2 melt. The La–Mn–O crystal grows gradually in molten salt with the increase of temperature. It was confirmed that LaMnO3- δ with perovskite structure and incomplete oxygen content were synthesized by molten salt method and presented a three-dimensional shape. LaMnO3- δ stores energy by redox reaction and adsorption of OH− in electrolyte simultaneously. In comparison with the stoichiometric LaMnO3 prepared by the sol–gel method, LaMnO3- δ prepared by molten salt method proffered higher capacitance and better performance. The galvanostatic charge–discharge curve showed specific capacitance of 973.5 F/g under current density of 1 A/g in 6 M KOH. The capacitance of LaMnO3- δ was 82.7% under condition of 5 A/g compared with the capacitance at the current of 1A/g, and the specific capacitances of 648.0 and 310.0 F/g were obtained after 2000 and 5000 cycles of galvanostatic charging–discharging, respectively. Molten salt synthesis method is relatively simple and suitable for industrial scale, presenting a promising prospect in the synthesis of perovskite oxide materials.