An alternative solution for designing power line conductive electromagnetic interference (EMI) filter by using the consecutive orthogonal array method is proposed. The circuit parameters of EMI filters to be determined are assigned as the control variables in the orthogonal arrays, and the average effects corresponding to each control variable are calculated from the measured results. In accordance with the inferential rules, the average effects are used as the observational indices to adjust the levels of the control variables of the subsequent orthogonal array. Through manipulating consecutive orthogonal arrays step by step, the applicable ranges of circuit parameters are approached with desired output performances. The design procedure and the inferential rules are described by illustrative examples for a single-stage high-power-factor converter.