Carbon loaded PtNi alloy nanocatalysts (Pt2.7Ni/C) were prepared by liquid phase synthesis using platinum acetylacetonate (Pt(acac)₂) and nickel acetylacetonate (Ni(acac)2) as precursors, tri-n-octylphosphine oxide (TOPO) as surface modifier, oleylamine (OAm) as reducing agent, N,N-dimethylformamide (DMF) as auxiliary, and superconducting carbon kochen black ECP as carrier. The morphology of Pt2.7Ni/C was characterized by TEM, the qualitative and quantitative analysis by ICP-AES, the structural characterization by XRD, and the electrochemical cathodic oxygen reduction catalytic performance was further investigated. It was shown that the particle size of the prepared Pt2.7Ni/C nanocatalysts were in range of 3-11 nm with an average size of ~6.25 nm. The mass activity of Pt2.7Ni/C nanocatalysts was 796.08 mA.mg-1Pt (4.0 times as effective as the commercial Pt/C(JM) catalysts) and the specific activity was 3.60 mA.cm2(11.3 times as effective as the commercial Pt/C(JM) catalysts) under acidic conditions when the potential was at 0.9 V (vs. RHE). The catalytic activity of the Pt2.7Ni/C nanocatalysts remained higher than that of the commercial Pt/C(JM) catalysts after 5000 and 10000 turns of accelerated endurance experiments, showing excellent oxygen reduction catalytic performance of the Pt2.7Ni/C nanocatalysts.