The CoSe₂ nanoparticles were first prepared through microwave synthesis, and followed by chemical reduction of Ru on the CoSe₂ surface. The transformation of orthorhombic to cubic CoSe₂ phase took place upon the subsequent heat treatment at 400 ℃, which led to the formation of (Ru_xCo_y)Se₂/C nanoparticles. A small amount of Ru introduced into the CoSe₂ significantly enhanced the activity of (Ru_xCo_y)Se₂/C toward oxygen reduction reaction, and high Ru utilization was achieved. The half-wave and open-circuit potentials were 0.68 V and 0.88V (vs. RHE), respectively, with the electron transfer number of 4.0 in 0.1 mol/L HClO₄. The mass activity of the (Ru_xCo_y)Se₂/C catalyst reached 0.09 mA/mg Ru at 0.75 V, which is comparable to that of the commercial Pt/C catalyst (0.10 mA/mg Pt). Only 15 mV decrease in half-wave potential was observed after 1000 cycles in 0.1 mol/L HClO₄, showing good stability.