This paper was undertaken to study a wide variaty of problems concerned with manufacturing Hydrogen Peroxide. By means of the laboratory experiments they were observed, a critical and comprehensive data, and optimum conditions for preparing Hydrogen Peroxide. The laboratory experiments were divided to three steps as follows. The first step; the diaphragm electrolytic process, in which ammonium peroxy-disulfate was formed on the anode by oxidation electrolytic. The second step; the Hydrolysis and Distillation process, in which Hydrogen Peroxide was formed by pure chemical reaction in the heated oxygenated anolyte, then the H₂O produced was separated directly from H₂O₂ anolyte mixture under vacuum distillation. The last step; the concentration of dil. Hydrogen Peroxide by fractional distillation under vacuum. The cell (1 liter glass cylinder)was consisted of two rectangular platinum anode lines and a rectangular platinum cathode plate dipped into a cylindrical porous ceramic diaphragm set in the center of the cell. Anolyte chamber (outside the diaphragm) was filled with 650 ㎖ solution containing 260 gr. of ammonium sulfate and 200 gr. of sulfuric acid per liter, and catholyte chamber (in the diaphragm), 125 ㎖. solution containing 230 gr. of ammonium sulfate and 280 gr. of sulfuric acid per liter. The electrolytic experimental data were demonstrated in Table 1 to 7, and their curves, on Fig. 9 to 15. Concentration process data were demonstrated in Table 8 to 10, and their curves, on Fig. 16 to 19. According to above data, maximum cEff. was obserrsed 83%, maximum eEff., 34%, and maximum concentration of H₂O₂. 56%.