NOVELTY - A catalyst is prepared by dissolving platinum or palladium containing compound in a solvent to obtain a solution; vacuum drying inorganic oxide carrier particles; dipping vacuum dried particles in the prepared solution; filtering; calcining filtered particles; subjecting calcined particles to hydrophobic treatment; immersing treated particles in a polyfluorotetraethylene solution; and heating.    USE - Method of preparing a catalyst (claimed) for closed secondary battery.    ADVANTAGE - The method prepares catalyst that is hard to sinter at high temperature, and having good dispersion and high catalytic efficiency; employs catalytic reaction device that is easy to operate and manufacture; and overcomes problems that carbon-supported platinum or palladium catalyst can not resist high temperature and oxidation.    DETAILED DESCRIPTION - A catalyst is prepared by:    (A) dissolving platinum or palladium containing compound in a solvent to obtain a solution (0.01-1 g/l);    (B) vacuum drying inorganic oxide carrier particles at 80-120 degrees C for 0.2-10 hours;    (C) dipping vacuum dried particles in the prepared solution for 1-10 hours;    (D) filtering and calcining filtered particles at 550-700 degrees C for 1-5 hours in a hydrogen reducing atmosphere with a temperature gradient of 2-15 degrees C/minute;    (E) subjecting calcined particles to hydrophobic treatment;    (F) immersing treated particles in a 5-30% polyfluorotetraethylene solution for 10-60 minutes; and    (G) heating at 330-370 degrees C for 0.5-1 hours in an inert gas atmosphere.    An INDEPENDENT CLAIM is included for a catalyst performance testing device comprising:    (1) a closed pressure-resistance insulated container having a catalyst loading component above an electrolyte;    (2) a platinum cathode and a platinum anode inserted in the electrolyte and are electrically connected with battery tester outside the closed pressure-resistance insulated container through a connection cable;    (3) a manometer and a safety valve set on the closed pressure-resistance insulated container;    (4) a temperature sensor set in the catalyst loading component and is electrically connected with the battery tester outside the closed pressure-resistance insulated container through a connection cable;    (5) a pressure sensor; and    (6) a thermograph fixed on the closed pressure-resistance insulated container, and having a probe set in the closed pressure-resistance insulated container above the liquid surface of the electrolyte (4).