The oxidation stability of four lowviscosity oils was evaluated by NB/SH/T 0811 method.The carbon composition of the oils was analyzed by SH/T 0725 method,and the effect of carbon composition on the oxidation stability of the oils was explored.The results show that the higher the content of nparaffin,the better the oxidation stability of the oils.The higher the content of isoparaffin or naphthenic hydrocarbon,the easier the oil is oxidized to produce acidic substances.The higher the content of aromatic hydrocarbon,the easier the oil is oxidized to produce deposit.The higher the content of naphthenic hydrocarbon and aromatic hydrocarbon,the better the solubility of oil to sludge.In order to improve the efficiency of oxidation experiment,the oxidation conditions of NB/SH/T 0811 method,such as oxidation time and catalyst were improved,and the influence of the change of oxidation conditions on the evaluation results of oxidation stability was explored.The results show that the change of oxidation conditions will not fundamentally change the evaluation results of oxidation stability of the oils,but different catalysts may have a special impact on a certain evaluation index