In order to predict the Radio Frequency Interference (RFI) level of HVDC-flexible converter valve, the topology of Modular Multilevel Converter (MMC) and its operation mechanism were analyzed. The radiation model of the valve tower was set up in this paper. Considering the changing states of the IGBT, the radiation model was time-variable. The far field directional diagram and field strength were calculated. The simulation results were compared with the measurement results and limit value in standard. The results showed that: as the frequency increases, the converter station RFI produced decreases in value, and the directivity gradually increased, the E-field strength of lateral side valve is higher than the longitudinal side valve and the value is within the limits.