For oil shale situ high-temperature mining, underground frozen wall should be constructed to prevent underground water flowing into the mining area and the leakage of oil and gas．The buffer zone between the high-temperature mining area and the freezing zone of underground frozen wall not only affects oil shale mining and frozen wall cooling effects but also affects the entire project construction and operating costs. By theoretical calculation method and numerical simulation, with the lowest cost as the goal, the detailed calculation and analysis are made and the rational buffer distance is determined, which could be the theoretical guidance to underground frozen wall design for oil shale in situ high-temperature mining.