The pore-fracture structure evolution of oil shale is the key factor for in-situ fluidization.At the beginning, with Xinjiang Balikun oil shale as test sample, the oil shale was pyrolyzed on an independently developed superheated steam action experimental system.Then, we combined micro-CT technique with scanning electron microscopy technique to test the pore-fracture characteristics of oil shale under temperatures effects, with the help of the Avizo software, to analyze the evolution of the pore-fracture structure, internal seepage field characteristics, and surface microscopic characteristics along with increasing pyrolysis temperature. The result show that: at first, the internal fractures of oil shale is mainly microfractures (100-500 μm). With increasing steam pyrolysis temperature，the number of microfractures increases exponentially，and the small holes gradually transform into middle or large holes. Then, as the temperature of water vapor increases, the porosity of oil shale increases significantly, raising from 2.7% at normal temperature to 16.2% at 555℃, which is six times that at room temperature. In addition, with the increase of pyrolysis temperature, the internal connected pores of oil shale are also increasing, providing a good channel for the transport of high temperature water vapor and pyrolysis products. In general, the permeability of parallel bedding direction is always greater than that of vertical bedding direction.Finally, there are obvious anisotropic characteristics of oil shale permeability. When the temperature is 314℃, the permeability of oil shale varies greatly between the parallel and vertical layer directions, and the anisotropic permeability can reach the order of magnitude of 103. The research conclusion is of great significance to regulating the process parameters of in-situ shale oil and gas production by steam convection heating.