The invention belongs to the technical field of electrochemistry, and relates to a symmetrical electrochemical capacitor which uses a sulphate water system electrolyte and takes the rice husk porous carbon as an electrode material, and has the maximum working voltage of 1.6V-1.8V. The water system symmetrical electrochemical capacitor consists of a positive electrode, a negative electrode, a membrane, an electrolyte, a positive wire, a negative wire and a shell, wherein the active materials of the positive and the negative poles are rice husk porous carbon, and the electrolyte adopts one or the mixed liquor of sodium sulfate, potassium sulfate, lithium sulfate and other sulphate aqueous solutions. The mass ratio of the positive and the negative electrodes is (1:1)-(1.5:1). The sodium sulfate, potassium sulfate, lithium sulfate and other sulphate aqueous solutions are adopted as the electrolyte, compared with adopting sulfate and potassium hydroxide electrolytes, the maximum working voltage of the electrochemical capacitor can be increased to 1.6-1.8V from about 1V, so the energy density of the water system symmetrical electrochemical electrical double-layer capacitor is greatly increased, and moreover, good stability is obtained; and compared with the organic electrolyte, the symmetrical electrochemical capacitor has the characteristics of low prices, no toxicity, no pollution, simplicity in operation and the like.