The invention discloses a method for increasing air-coupled 
ultrasonic detection signal strength of a 
composite material. The method comprises the following steps: step one, placing a workpiece between a first air-coupled 
transducer and a second air-coupled 
transducer; step two, sticking two thin 
layers on the upper and the lower surfaces of the workpiece; step three, stimulating the first air-coupled 
transducer, enabling the ultrasonic 
waves emitted by the first air-coupled transducer to pass through upper side air, the upper side 
thin layer, the workpiece, and the lower side 
thin layer and lower side air in sequence, and reaching to the second air-coupled transducer; and step four, feeding back a 
signal received by the second air-coupled transducer to a computer and generating an image and data; the invention provides a method and technology for conducting 
impedance matching on the detected workpiece, so that ultrasonic 
waves reflected back and forth in the thin 
layers are kept in the same phase when transmitting the thin 
layers, so as to realize the enhanced energy transmission effect similar to the 
resonance and improve the detection sensitivity of a whole detection 
system, and 
thin layer materials can be recycled.