The modular multilevel converter(MMC) and dual active bridge converter(DAB) system offer several advantages, such as flexible control, electrical isolation, and low electrical stress. These characteristics make it a promising choice for future distribution grid systems. However, due to the numerous switching devices within the system, it generates EMI noise and has a complex structure, resulting in a highly intricate internal electromagnetic environment. Consequently, establishing EMI prediction models for this system is challenging. To accurately predict the conducted EMI of the MMC-DAB system, this paper focuses on analyzing the influence of high-frequency parasitic parameters of the internal transmission line. The study reveals that the unbalanced line impedance converts a portion of common-mode(CM) current into differential-mode(DM) current, leading to the EMI spectrum of the system. By comparing the EMI spectrum obtained through predictive modeling with the tested spectrum of the prototype, the two spectra exhibit a high degree of agreement, validating the study ' s rationality and credibility.