The invention discloses a true triaxial gas-liquid-solid coupled coal sample wave velocity anisotropy detection device and method. The device comprises a pressure-bearing cavity body, a gas transmission system, a coal sample placement table, a true triaxial pressurization system, a transducer set, an acoustic wave instrument and a humidification system; the pressure-bearing cavity body is composedof a pressure-bearing container with an opening in the upper part and a piston top cover; a plurality of axial pressure rods of the true triaxial pressurization system penetrate through the side walls of the pressure-bearing container and the piston top cover to be in contact with the four side surfaces and the top surface of a test coal sample; the gas transmission system comprises a vacuum pump, a safety gas cylinder and a high-pressure gas cylinder; and the humidification system comprises a control host, an electric control water jet pump, a humidity sensor and a water spray nozzle. According to the detection device and method, the real situation of a coal body in deep underground can be simulated, so that the characteristics of ultrasonic wave velocity anisotropy under the influenceof different gas pressures, different humidity and different triaxial loading stresses for coal samples with different physical and mechanical properties are obtained, and the theoretical support is provided for subsequent coal mine exploration and exploitation.