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A comparative analysis is made of the shielding failure rates obtained with IEEE and DL/T620’s formulas, and a regionalization is conducted on the shielding failure rate over Chongqing with the data of LLS (Lightning Location System) from 1999 to 2008 The results show that the shielding failure rate increased with the increasing rolling sphere radius. When the rolling sphere radius was the same, the shielding failure rate provided by IEEE was higher than the reality and lower than that by DL/T620’s. When the rolling sphere radius was lower than 120 m, the shielding failure rate provided by IEEE was lower than that by DL/T620; on the contrary, the shielding failure rate provided by IEEE was higher than that by DL/T620’s. The shielding failure rate provided by IEEE was close to the reality. Based on that, a satisfactory shielding failure rate expression is given, with which the shielding failure rates of various types of buildings are regionalized. The results can be used as theoretical bases for lightning disaster risk assessment and lightning protection design.