Abstract: This paper introduces a new non-contact ultrasonic testing technology and its application based on optical microphone. The optical microphone is based on the effect of the acoustic field on the light refractive index to carry out the acoustoelectric energy conversion, which replaces the traditional acoustic sensor to complete acoustoelectric energy conversion by inducting vibration, and thus makes the optical microphone has excellent bandwidth and sensitivity. The reliability and advantages of the technology are verified by testing applications in automotive structure spot welding and honeycomb sandwich composites.