Abstract: When residual oil is in stationary and ruining, we rate the corrosion speeds to Q235 steel by a-handy instant corrosion speeds measuring. After we alter the content of naphthenic acid in residual oil, comparing the corrosion speed when residual oil is in stationary and running. Consequence shows that the corrosion speeds in ruining is greater than in stationary, when running speeds is greater, the corrosion speeds is faster, the corrosion speeds is faster with the rising of the content of naphthenic acid.