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 H-2-temperature-programmed reaction were investigated as potential catalysts for preferential CO oxidation (PROX) in excess H-2 at high temperatures. It was found that the catalytic activities of these Co2P/gamma-Al2O3 catalysts were related to their Co loadings. The CoP-10 catalyst showed the best PROX performance in temperature range of 220-240 degrees C, which was attributed to its optimal microstructures (high surface area, small particle size and big amount of active site).