Conducted electromagnetic interference has been analyzed in many papers, and few papers deal with the problem of radiation 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, the product it is difficult to through the standard radiation electromagnetic interference, so it is necessary to establish general radiation EMI model, and measure the relevant noise and its analysis, and more intuitive to solve the problem of radiation 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 radiation EMI characteristics of the converter. Finally, the theory and technology proposed in this paper are verified through experiments.