Preferential oxidation (PROX) of carbon monoxide is considered to be the most effective method for selective removal of the trace of CO in excess hydrogen. Although the precious metals have exhibited outstanding catalytic performance, in view of their less availability, higher price, and worse practicality, replacing them by non-precious transition metals is a desirable route, which has a broad development scope. In this paper, the latest research progress in the use of non-precious transition metals for the preferential oxidation of CO in excess hydrogen is summarized. Based on existing research findings we may safely foresee that non-precious transition metal oxides might be the promising catalysts for preferential oxidation of CO in excess hydrogen, which could play an important role in the hydrogen purification to provide high-pure hydrogen source for proton exchange membrane fuel cells.