Abstract: The invention relates to the technical field of in-situ development of shale oil resources and consists of a device and technique for simulating the propagation of shale fractures under the influence of high-temperature convective heat. The apparatus is comprised of a data collecting and processing system, a high-temperature thermal fluid generator, a high-pressure pumping device, and a shale reactor. The thermal fluid generator for high temperatures consists of a fluid generator, a temperature controller, and a pressure controller. The shale, reaction kettle consists of an outer chamber, an outer chamber lid, a scaled rock cavity, and a shale sample. The outer cavity cover of the reactor is fitted with a simulated wellbore, the bottom end of the simulated wellbore penetrates the inner cavity cover and extends to the interior of the shale sample, and the top of the simulated wellbore is connected to a high-pressure constant-speed injection pump.