Abstract: Coupling pressure is a key factor affecting the detection effect of ultrasonic excitation infrared thermography, and the coupling pressure loading device indirectly controls the excitation effect by influencing the coupling pressure in ultrasonic excitation. In this research, the ultrasonic thermal excitation test of concrete microcracks under different loading methods of coupling pressure was carried out, and the temperature field of microcracks under the action of 900, 1200 and 1500 N initial coupling pressure was analyzed through the comparative study of direct loading and aluminum alloy limiting device loading, and it was concluded that the temperature rise effect of directly loaded concrete was better than that of aluminum alloy limiting device under different loading methods of the same initial coupling pressure. This is due to the fact that the aluminum alloy loading device acts on the transducer by more than 50% of the additional force disturbance increment during the excitation process, and the equivalent resistance of the transducer changes drastically, resulting in the deterioration of the working stability of the ultrasonic excitation system, and then weakening the ultrasonic thermal excitation effect. Subsequently, the force disturbance of the loading device on the excitation transducer should be weakened, and the coupling pressure low disturbance loading device with the stiffness of the system adapted to the high-frequency excitation behavior of the transducer should be studied to achieve the efficient output of sound energy of the ultrasonic excitation system.