In this study we provide a simple method to synthesize single crystalline PtCo nanoparticles with cubic shapes.The key factor to formation of cubic morphology is using Mo(Co)6 as a reducing agen.As-synthesized PtCo nanocubes with size that are close to 7-10 nm.A phase transformation from the originally disordered face centered cubic (FCC) structure to an ordered face centered tetragonal (FCT) structure occurred after annealing.The phase analysis, structure, and magnetic properties were determined by X-ray diffraction (XRD), High resolution transmission electron microscope (HRTEM), Scanning electron microscope(SEM) and vibrating sample magnetometer (VSM) techniques.