A new low cut-off voltage ring cathode electron gun model is presented in this paper. On the basis of traditional Pierce electron gun and pole-controlled electron gun, the spherical cathode is divided into annular emitting cathode and non-emitting cone to achieve lower focusing pole cut-off voltage, reduce switching loss of modulator unit and increase the maximum modulation frequency. The results show that the cut-off voltage of the cathode can be reduced by half by the introduction of nonemitting cone under the condition of perveance 0.53 μP, the cut-off voltage amplitude is reduced to 600 V from 1 250 V, the modulation loss of the corresponding power modulator is reduced to 1/4, or the modulation frequency is increased by four times, which is of great significance to the improvement of electronic countermeasures and radar system performance.