Pt nanoclusters (NCs) with diameters of 1-3 nm are regarded as one of the most promising high performance oxygen reduction reaction (ORR) catalysts. However, the application of such small Pt NCs is always limited by the preparation methods and the stability of Pt. In this work, an efficient and stable ORR catalyst was prepared by assembling unprotected Pt NCs (similar to 1.4 nm) on ordered mesoporous carbon (OMC) via a facile strategy. The as-prepared Pt NCs/OMC (Pt loading: 10 wt %) exhibited more desirable ORR catalytic performance. The specific activity (SA) and mass activity (MA) of Pt NCs/OMC at 0.9 V were 2.73 and 3.81 times higher than those of the commercial Pt/C (Pt loading: 20 wt %) in 0.1 M HClO4. Meanwhile, the Pt NCs/OMC exhibited more satisfactory stability. The Pt NCs/OMC displayed relatively slight losses of 2.3% in MA and 2.7% in SA after the 1500 cycles accelerated stability test, in contrast to respective losses of 35.8% and 37.2% for the commercial Pt/C. In consideration of the enhanced catalytic performance and excellent stability, the as-prepared Pt NCs/OMC demonstrates great potential as a practical ORR catalyst.