The invention relates to an indoor simulation device and method for supercritical water and shale reaction. The device comprises a high-temperature and high-pressure reaction kettle, a vacuum pump, anair compressor, a booster pump and a heating device. The high-temperature high-pressure reaction kettle consists of a kettle body, a kettle cavity, a kettle cover, a rock core jacket and a filter screen bracket, wherein the kettle cavity is formed in the kettle body, the upper part of the kettle cavity extends out of the kettle body, the kettle cover is mounted at the top of the kettle cavity, pressure fluid is injected through a communication valve port to realize rock core confining pressure control and is placed on a filter screen bracket at the bottom of the inner side of the kettle cavity, and the filter screen bracket is vertically arranged in the middle of the bottom of the kettle cavity and used for placing a rock core jacket; the heating device is arranged on the outer side of the kettle cavity; a gas injection pipeline, a gas exhaust pipeline and a detection pipeline are arranged on the kettle cover, penetrate through the kettle cover from the kettle cavity and extend to theoutside, and the gas injection pipeline is connected with the booster pump. According to the invention, under a specific gas environment, a rock sample can react with water under the condition of exceeding the critical temperature and pressure of water, and indoor simulation of shale and supercritical water reaction is completed.