The invention discloses a device and method for simulating gas flowing of a matrix-crack system. The device comprises a gas pressurizing injection system, a model system, a constant temperature control system and a metering system which are sequentially connected, and the gas pressurizing injection system comprises a gas source tank and a pressurizing mechanism for pressurizing gas flowing out ofthe gas source tank; the model system comprises three stages of rock core gripper connected in series, a confining pressure pump for providing the confining pressure for each stage of rock core gripper, and pressure gauges arranged at the inlet ends of the rock core grippers correspondingly; the three stages of rock core grippers are sequentially filled with matrix rock cores, natural crack rock cores and manual crack rock cores; and the constant temperature control system is arranged outside the model system and used for simulating the formation temperature; and the metering system comprisesa flow meter arranged at the outlet end of the last stage of rock core gripper, and a temperature sensor. Flowing of the gas in the reservoir matrix-crack system can be simulated under high temperature and high pressure conditions.