In order to achieve the commercialization of proton exchange membrane fuel cells (PEMFCs), it is necessary to synthesize electrocatalyst with higher electrochemical activity. In this study, PtCo nano-alloy electrocatalyst was prepared by liquid phase synthesis method with sodium borohydride as reducing agent, triethylamine as complexing agent, and by sequential heat-treatment. The physical properties of the catalyst were characterized by different analytical methods. We studied the effects of heat-treatment temperature, different amounts of sodium borohydride and triethylamine on electrochemical performance. The results show that heat-treatment can greatly improve the mass activity of the catalyst, and 500 ℃ is the optimal temperature for preparing the catalyst with the highest catalytic performance towards oxygen reduction reaction(ORR). Compared with commercial TKK-PtCo alloy catalyst under the same test system, the as-prepared catalysts exhibits advantages of more uniform particle size distribution, smaller particle size and higher electrochemical performance. In particular, the mass activity (MA) of the prepared catalyst is 133 mA/mg_Pt, which is 3 times of TKK-PtCo alloy catalyst.