Conducted electromagnetic interference has been analyzed in many papers, and few papers deal with the problem of radiated electromagnetic interference. However, as the switching frequency increases, wide bandgap devices became popular, the radiation generated by the power converter electromagnetic interference becomes more and more serious, and the product is difficult to pass the standard radiated electromagnetic interference, so it is necessary to establish a general radiated EMI model, and measure the relevant noise and its analysis, and more intuitively solve the problem of radiated EMI. Therefore, this paper develops a radiation model based on the flyback converter, and then studies the relationship between the radiated noise current and the radiated electric field on the basis of this model, and designs a current transformer to measure the noise and evaluate the radiated EMI characteristics of the converter. Finally, the theory and technology proposed in this paper are verified through experiments.