Abstract: Abstract：The Dayishan fault, flaked on the north and south by the N-S-trending Shuikoushan-Xianghualing tectonic zone, belongs to the southeastern segment of the NW-trending Shaoyang-Chenzhou fault. On the basis of the characteristics of tectonic deformation, combined with the regional tectonic setting and evolution, the authors consider that the Dayishan fault experienced at least three tectonic movements in the Meso-Cenozoic, which are from early to late times the Indosinian sinistral strike-slip movement, Yanshanian dextral strike-slip movement and Himalayan (?) sinistral strike-slip movement. After an intensive analysis of the ages of the N-S-trending structure and NNE-trending regional structure and their interaction, the authors propose the following new idea of the genesis of the N-S-trending structure：as the basement sinistral strike-slip movements of the NW-trending Dayishan fault and Xianghualing-Yangmingshan fault occurred in the Indosinian movement, the E-W compressional stress field derived by the strike-slip motion and sinistral drag produced by the strike-slip motion led the regional NNE-directed lineament to rotate counterclockwise, thus forming the N-S-trending structure. Further analysis suggests that the Indosinian was probably a period of the strongest movement of the main NW-trending faults in eastern Hunan in the Mesozoic, and that sinistral strike-slip motions of several NW-trending faults in the Indosinian ａｒｅ probably one of the formation mechanisms of the Xｕefengshan arc structure and the Qiyang “epsilon”-type structure.