Abstract: The lost circulation problem often brings about great challenges to petroleum engineering sector, especially in the case of encountering fractured strata with stress?sensitivity while drilling deep wells. By means of core soaking experiment and conventional rock mechanics experiment under simulated formation conditions, this paper tests the rock mechanics parameters of fractured carbonate rocks after soaked by plugging slurry, and analyzes the samples’mechanics strength weakening effect and plugging mechanism. Considering the stress?sensitivity differences caused by the fracture and pore structure characteristics, this paper quantitatively analyzes and discusses the lost circulation law of such a formation, providing a theoretical basis for the plugging mechanism study of stress?sensitivity fractured strata