A facile, reliable, and robust synthetic method to prepare high-quality Pt-3 Fe nanocubes is reported. Results of investigation on these Pt-3 Fe nanocubes in shape-/size-distribution, crystallinity, structural characteristics, compositions, electrochemical activity towards small organic molecule oxidation as well as capability of assembling into simple cubic supercrystals are presented, and a possible formation mechanism of the cubic nanocrystals at high temperature in oleylamine/oleic acid solution is also proposed. This study indicates that the catalyst performance may be improved by controlling the shape of particles.