The electric field in a horizontally polarized bounded-wave electromagnetic pulse(EMP) simulator with 9.5 m in height are got by experimental measurement. The study of field distribution characteristics in the simulator based on the field, including the quantity analysis of the field uniformity in some domain and the method for defining the effective testing space in the simulator, is given. The domain of an effective space with the lowest horizontal plane 2 m away from the ground is estimated. The experimental results show that, the peak-value of the electric field of the testing point right under the bicone’s center with a distance of 5.5-7.5 m decreases inversely with the distance between the testing point and the bicone’s center. The effect of the discontinuous configuration of the bicone and the plane on the electric field in time domain of the testing points under the center is slower as the distance increases, but the influence of the ground on the field is quicker; The field along the leakage direction of the field in the simulator decreases more slowly than those along the bicone’s symmetric axis, as the testing-points located at a horizontal plane far away from the ground; The mean value of the normalized electric field in 12 m×12 m domain on the horizontal plane 1 m away from the ground in the simulator is 0.678, the corresponding standard deviation is 0.068 9, and the field uniformity is 2.039 dB.