The Chenghai Fault Zone, as the eastern boundary fault of the Dali Rift System, has experienced multiple phases of tectonic evolution since the Cenozoic. During the Early Cenozoic, the Chenghai Fault Zone accommodated part of the eastward extrusion of the Tibetan Plateau through thrust nappe structures. Since the Pliocene, the fault zone has transitioned to transtensional deformation. However, there is ongoing debate regarding the initiation of this transtensional activity and the characteristics of faulting in the southern segment. This study, utilizing remote sensing interpretation, field geological investigations, paleo-tectonic stress field inversion, and focal mechanism solutions, delineates the spatial geometry, activity, and tectonic stress field of the Chenghai Fault Zone's Qina-Binchuan segment since the Pliocene. By integrating previously published geochronological data and seismic records, a tectonic evolution model of the Chenghai Fault Zone since the Pliocene is proposed. The results reveal a migration of fault activity within the southern segment of the Chenghai Fault Zone. The Qingshui-Zhoucheng Fault in the southwestern area exhibited significant activity before the Middle Pleistocene, but its activity has markedly decreased since the Late Pleistocene. Currently, the Bincuan Fault in the southeastern sector shows the highest level of activity, indicating an eastward migration of faulting in the southern segment. Analysis of the fault zone's geometry and stress field inversion suggests that the Chenghai Fault Zone has undergone rotational deformation since the Pliocene. Considering the regional tectonic context, this rotation is interpreted as a tectonic response to the clockwise rotation of the Dali Rift System. This study provides crucial insights into the migration of fault activity during the evolution of strike-slip fault systems and enhances the understanding of the mechanisms by which microblock rotation accommodates deformation during the extrusion of plateau material.