Abstract: Using the potcnlioslatic and the kinetic methods,the promotion of ruthenium on the clectrocatalytic oxidation of trace carbon monoxide on Pt/C in 1N H₂SO₄ was investigated.The results indicated that ruthenium can not only increases the clectrocatalytic activity of platinum,but also inhibitcs greatly the poisoning of the catalyst.Amechanistic model was proposed to explain the behaviour of ruthenium.