Abstract: The horizontally polarized radiated-wave antenna with biconical-wire grating structure has less influence on the half-width of radiated E-field，and it is easy to erect and maintain. Mastering the E-field distribution rule is a premise to determine the simulator's uniform area and conduct the EMP effect experiment.The distribution rule of the radiated E-field is studied using the antenna theory，and the analysis results are verified by simulation and practical experiment.It shows that the polarized E-field component below the biconical apex is only inversely proportional to the distance from the observation point to the excitation source if the antenna structure and excitation voltage are determined.On Oxz plane，the polarized E-field amplitudes on a circle centered at the biconical apex are equal. And they reach the peak value at the same time.On Oxz plane，the total E-field amplitudes at the observation points on a horizontal line are equal，and their directions are along the tangent line of an arc where the observation points is located.The E-field components are symmetrical with Oxz and Oyz planes.As for a practical simulator，the ground reflection causes severe decline in the falling edge of the radiated E-field，which reduces the half-width of the radiated field near the ground. Meanwhile，the wire grating plate also affects the radiated field nearby，and the reflections are stronger at four angular points of the plate.The distribution of radiated fields at other points is consistent with theoretically analyzed result.

Key words: radiated-wavesimulator, electromagneticpulse, biconical-wiregratingantenna, electromagneticfield, numericalsimulation