Based on the terminal port theory, this paper has proposed a common-mode conducted noise modeling method. Single-phase inverter is chosen as an illustrative example. The T-type model has been supposed as the internal structure of the terminal port, according to its features of CM impedance and the noise propagation route. The details of equivalent noise source are given and its accuracy has been verified by comparing with the concept definition. With this model, the effectiveness of the filter could be predicted quickly and accurately. The interaction effect between the EMI filter and harmonic filter has also been viewed in this paper. Theoretical analysis and experimental results are presented to verify this modeling methodology.