Using the synchronous slow electric field data at 7 stations of high precision GPS clock in Datong region of Qinghai Province in 2009, the electric field change are fitted based on the point dipole model, and nonlinear least square and exhaust algorithm methods, the field changes for 26 times of return strokes happened in 11 negative ground flashes during the field observation of 2009 were fitted, it aims to solve for the correction coefficients of slow antenna at different stations taking Mingde station as the standard, namely, how environmental factors, such as altitude and vegetation cover influence on the slow antennas at each station. At the same time, the locations of dipole moment and the moment center of the charges neutralized return strokes at each times are obtained with help of mean correction coefficients at each station. The results show that the antennas are amplified or shielded by environmental factors in varying degrees, and the correction coefficients of slow antennas are closely related to natural factors on the Plateau. The vertical component of the dipole moments neutralized by return strokes of the negative ground flashes are 11.6～66.0 C·km^-1, the moment centers are 1.6 to 6.8 km.

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