A PtSn nanocatalyst supported on carbon (PtSn) was prepared with the enhancement of the extent of alloy degree of Pt with Sn by the heat treatment at 300 degrees C in a nitrogen atmosphere (PtSn/C-HT). The PtSn and PtSn/C-HT catalysts prepared were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and electrochemical methods, and were tested as an electro-catalyst in ethanol electro-oxidation. Results showed that the average particle size of the PtSn/C-HT was increased by the heat treatment, compared to that of PtSn. The catalytic activity of PtSn/C-HT, however, was superior in ethanol electro-oxidation. The enhanced catalytic activity of PtSn/C-HT was attributed to both the high degree of alloying in the PtSn structure and the extended Pt lattice, which promote catalytic activities in ethanol electro-oxidation and removal of intermediate CO species.