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.