Today the electrochemical chlor-alkali process is the most common method for simultaneous production of chlorine gas and caustic solution, which accomplishes by three methods of mercury process, diaphragm process and membrane process. Among these the membrane chlor-alkali technology is the most economical and environmental friendly method. Therefore other methods will be forced to change to membrane process in future. However the membrane chlor-alkali process is one of the most expensive processes in chemical industries from the energy consumption point of view. Therefore studies for reduction in energy consumption of this process have led to major improvements in the structure of this process. By replacement of hydrogen generating cathodes with porous and diffusible oxygen reduction cathodes and change in the cathodic reaction of the process, necessary cell voltage and therefore energy consumption can be reduced as much as 30% at current density of 0.4 A/cm 2 . Chlor-alkali process using oxygen reduction cathode known as advanced chlor-alkali process, despite of considerable reduction in the energy consumption for mass unit, has some drawbacks. The most important problem along with advanced chlor-alkali process is production of an undesirable intermediate product called hydrogen peroxide which is generated by a secondary oxygen reduction reaction. Hydrogen peroxide can cause serious problems during the operation of the cell by intensifying corrosion of the cathode surface and sodium peroxide precipitation on this electrode at high sodium hydroxide concentrations. The main goal of this project was synthesis and evaluation of the performance of an alloy catalysis with capability of preventing from the undesired production of hydrogen peroxide for application in the advanced chlor-alkali process. To this aim at first nano size particles of alloy catalysts of perovskite La 1-x Ca x MnO 3 were synthesized by modification in one of the most recent methods for synthesis of nano particles to increase the surface area of the catalyst particles. Then the structure and chemical composition of the synthesized catalyst particles were characterized by different characterizations test methods. Also the efficiency of the nano size catalyst particles was evaluated before and after manufacturing of oxygen diffusion cathode for preventing from production of unwanted hydrogen peroxide product. Experimental evaluations showed that the synthesized catalysis of La 0.4 Ca 0.6 MnO 3 with specific surface area of 40 m 2 /gr, beside preventing from production of the mentioned unwanted product was able to reduce the energy consumption of the advanced chlor-alkali cell by working at the ideal voltage of 2.25 volt. In Addition, the modified