NOVELTY - Preparing proton exchange membrane fuel cell catalyst comprises (i) preparing cobalt particles by reducing cobalt(II) chloride hexahydrate; (ii) preparing cobalt-ruthenium core-shell nanoparticles by reducing ruthenium(iii) chloride and cobalt particle suspension solution by using ethylene glycol; (iii) preparing a ternary core-shell cobalt-ruthenium platinum/carbon catalyst by reducing chloroplatinic acid, the cobalt-ruthenium core-shell nano particles and mixed suspension solution by using ethylene glycol; and (iv) adding acid to adjust the pH, and performing solid-liquid separation.    USE - The method is useful for preparing proton exchange membrane fuel cell catalyst (claimed).    ADVANTAGE - The catalyst has low amount of platinum, and high catalysis activity.    DETAILED DESCRIPTION - Preparing proton exchange membrane fuel cell catalyst comprises (i) preparing cobalt particles by reducing cobalt(II) chloride hexahydrate, adding polyvinylpyrrolidone ethanol solution into ethanol solution of cobalt(II) chloride used as a stabilizer, slowly adding sodium borohydride ethanol solution under stirring condition for preparing nanocrystalline cobalt particles, and carrying out solid-liquid separation to obtain cobalt nano particles; (ii) preparing cobalt-ruthenium core-shell nanoparticles by reducing ruthenium(iii) chloride and cobalt particle suspension solution by using ethylene glycol: dispersing cobalt particles in ethylene glycol, stirring and adding polyvinylpyrrolidone as stabilizer, stirring for 30 minutes, gradually adding ethylene glycol solution of ruthenium(iii) chloride, mixing uniformly, adjusting the pH of the solution using sodium hydroxide to 11-12, raising the temperature to 100-120 degrees C, reacting for 4 hours, cooling, and carrying out solid-liquid separation to obtain cobalt-ruthenium core-shell nanoparticles; (iii) preparing a ternary core-shell cobalt-ruthenium platinum/carbon catalyst by reducing chloroplatinic acid, the cobalt-ruthenium core-shell nano particles and mixed suspension solution by using ethylene glycol: dispersing nanoparticles in the ethylene glycol, adding polyvinylpyrrolidone as the stabilizer, stirring for 30 minutes, gradually adding ethylene glycol solution of chloroplatinic acid, mixing uniformly, adjusting the pH of the solution with sodium hydroxide, raising the temperature to 100-120 degrees C, reacting for 2-4 hours, then adding X-72C carbon black, dispersing carbon paste in ethylene glycol, stirring and reacting for 1-2 hours, and cooling; and (iv) adding acid to adjust the pH of the solution to 3-5, and performing solid-liquid separation. The fuel cell catalyst comprises a conductive carrier and ternary core-shell structured nano particle.