Abstract: The radiation field of large biconical-ellipsoid cage antenna on ground and excited by a double-exponential pulse is studied and analyzed based on parallel finite-difference time-domain (FDTD) method with coaxial feed. The influence of several key parameters such as the cage radius, bicone half angle, the height of the antenna and the length of the antenna etc on the radiated electric field of the antenna is presented. Numerical results show that there is very little effect on the peak-value and rise-time of the radiated fields of testing points directly under the bicone center and the points along sideward departure from those points as the radius of the cage increases from 3.0 m to 4.5 m; the peak-value, rise-time and full width at half maximum (FWHM) of testing points may be affected by the bicone half angle; the field distribution uniformity on the horizontal plane with the same distance from ground is better as the height of the antenna increases; the field distribution uniformity of the edge region near the ellipsoid cage of the testing area on the plane including the central axis and perpendicular to the ground is better, as the distance between the two centers of the two circles got by the connection of two cages and the ground increases; there’s no linear increase for FWHM of testing fields as the source FWHM increases.