Novel alumina-supported cobalt phosphide catalysts (designated as CoP-3, CoP-10, CoP-20 and CoP-40) prepared from the precursors with Co loadings of 3, 10, 20 and 40 wt% by H2-temperature-programmed reaction were investigated as potential catalysts for preferential CO oxidation (PROX) in excess H2 at high temperatures. It was found that the catalytic activities of these Co2P/ c-Al2O3 catalysts were related to their Co loadings. The CoP-10 catalyst showed the best PROX performance in temperature range of 220–240 C, which was attributed to its optimal microstructures (high surface area, small particle size and big amount of active site).