Researches about factors affecting on the carbon brush wear ratio of a DC motor have been studied in detail but they were for finding out the related factors or analyzing them statistically. To solve these problems before this paper, it has already been verified that the carbon brush wear is increased proportionally according to A(current)×RPM×BT(Brush temperature). But in case of DC motors which have the one-biased wear, the effect of the ANT factor was not applied to exactly with dispersion errors, In this paper, it shows that the sum of wear ratios about both brushes is constant in proportion to the ANT factor. It is very important solution in verifying the effect of the ANT factor which was not trusted due to any external factors. Therefore, the main objective of this study is to confirm the correlation about the one-biased wear ratio of the positive and negative brushes with the ANT factor