Abstract: The magnetic flux leakage testing instrument is widely used to detect the atmosphere tank′s floor and outside of pipeline.But when the instrument′s channel consistency is terrible,the results are difference.Now nothing about channel consistency can be found in the standards and no indicators about it appears on the instrument itself.In order to find the relationship of the result and channel consistency,an experiment is done by two types of MFL instrument operating on the standard specimen.According to the analysis on the results,a way to evaluate the channel consistency about the signal deviation and the rate of linear deviation was found.When the signal and the rate of linear deviation are small,the channel consistency is well.Lastly the research can provide reference for supplement to the instrument′s performance parameter and the addition of MFL detecting standard.