This paper newly attempts to propose a method for compensating the mode-conversion by double negative (DNG) material, for establishment of SI performance and suppression of imbalance (common-mode: CM) component and EMI generated by differential-paired lines with bend discontinuities. To demonstrate the impact of the DNG material on CM component, the simulated Scd21, which is defined as the conversion from differential-mode (DM) to CM, are evaluated. The significant suppression effectiveness of Scd21 in the case study is achieved around 100MHz by DNG material. The suppression effectiveness at 70MHz is 10dB. It is estimated that the proposed structure is suitable for improving the SI performance and suppressing the CM in the case study. The results validate the proof of concept. The proposed method is good candidate for suppressing mode-conversion due to phase-difference.