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An analysis is made of the effect of tall buildings on the thunderstorm electric fields by using the finite difference method. The results show that: (1)The atmospheric electric fields are greatly affected by surrounding buildings; for example, the field intensities at the top of a 40m〖WTBX〗×〖WTBZ〗40m building (at the center point of its flat roof) with the heights of 10, 20, 50, and 100 m are about 1.4, 1.7, 2.8 or 4.5 times greater than that on the ground surface without any building, respectively. (2) The field intensity at the ground level in the immediate vicinity of the building is reduced relative to the case without buildings, with this shielding effect becoming negligible at horizontal distances from the building exceeding about 3.5 times of the height of the building. Therefore, the errors caused by the tall buildings should be considered in the measurement of thunderstorm electric fields.