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It is always difficult for a lightning protection project to build a qualified and economical earthing device for the areas with high soil resistance. Considering the relation of the shape of earthing electrodes to the utilization efficiency of materials and the difficulty in construction, the polygonal divergent earthing electrode technique is presented. The experiments on the technique were conducted at three sites with different environments. The comparison with common earthing devices indicates that the polygonal divergent earthing electrode technique is superior in the areas with high soil resistance. Comparisons are also made between the different installation distances and different dosages of resistance reducing agents. Thus, the optimal installation method is found out; the parallel connection coefficient is calculated on the basis of the experiment data; and the estimating method of engineering work load is obtained.