The invention discloses a coal gas adsorption/desorption diffusion simulation experiment device under different stress constraint conditions. The device comprises a stress loading system, a constant temperature system and a gas path system, wherein the stress loading system comprises a stress loading testing cylinder which is provided with a pressurization opening, a temperature measuring opening and a gas inlet, wherein the pressurization opening is connected with a stress loading device, a temperature sensor is arranged at the temperature measuring opening and the gas inlet is connected with the gas path system; the constant temperature system comprises a constant temperature box in which the stress loading testing cylinder is arranged; the gas path system comprises a high-pressure gas cylinder, a pressure reducing valve, a stop valve, a gas inlet pipeline, a pressure sensor, a gas outlet pipeline, a vacuum pump, a flow sensor and the like; and the temperature sensor, the pressure sensor and the flow sensor are connected with an industrial personal computer respectively through data acquisition modules. The device can be used for simulating and testing coal gas adsorption/desorption diffusion behaviors under the different mining stress constraint conditions in actual coal mines, thereby providing the basis for researching the coal gas migration rule, the gas emission and the other theories.