In this work, a novel synthetic strategy of PdAg nano-alloy colloids was established via methanol reduction, a environmental friendly method due to the advantage of biodegradable methanol. The obtained nano-alloys were decorated on the surface of graphene (Gr/PdAg). Gr/PdAg was then modified onto the surface of glassy carbon electrode (Gr/PdAg/GCE) to explore its electrocatalytic performance for brucine. The linear range of the electrochemical determination for brucine is 0.63 mu M-1.89 mM and the detection limit is 0.10 mu M. It was also used for the determination of brucine in human urine with recoveries from 95.0 to 104.0 %.