Abstract: Air-coupled ultrasonic testing technology, possessing the characteristics of non-contact and non-destruction, is widely used in nondestructive detection for materials. An air-based line-focus air-coupled ultrasonic transducer was designed and fabricated according to the measurement of crystalline silicon solar cells. Compared to the ultrasonic transducer based on the traditional polymer matrix, the air-based line-focus air-coupled ultrasonic transducer adopted the 3D printing method to hollow out the polymer matrix frame, which will further reduce the acoustic impedance of piezoelectric composites. The center frequency of the transducer is about 150 kHz, and the focus radius is 20 mm, aperture is 28 mm. The generating and receiving performance of the transducer was measured. An crack detection experiment was implemented on a monocrystalline solar cell by air-coupled Lamb waves. The crack can be located by analyzing the amplitude of the received signals, furthermore, a correlation analysis was performed to extract the characteristics of the cracks.