Mesoporous carbons (MPCs) with high specific surface area were synthesized by the heat-treatment and subsequent acid treatment of magnesium citrate. The MPCs obtained were examined as electrode materials for electric double layer capacitor and showed the huge gravimetric capacitance with superior rate performance in sulphuric acid electrolyte. The MPCs also realize the larger capacitance than conventional activated carbon in organic electrolyte and extraordinary high retention of capacitance at very low temperature, such as 80% of room temperature value at −60°C.