Abstract: The slope-based fault modeling method is a good solution for soft and hard fault diagnosis problems. But it is not applicable to practical circuit fault diagnosis due to the influence of tolerance. Several tolerance handling methods are given in this paper. First, the public point of slope feature curves is not a fixed value but derived from the actual circuit under test CUT. Hence, the tolerance information is contained in the public point. Secondly, due to the influence of tolerance， the slope feature of a potential fault component is not a sole value but a fan-shaped area. This fan-shaped area can be obtained by using either analytical method or simulated method. The proposed methods solve the tolerance influence of slope-based fault diagnosis methods.