This paper describes a method of laser ultrasonic propagation imaging based on Hilbert transform. The ultrasonic signals are excited by pulsed laser on the measured material surface. Then ultrasonic signal is transformed by Hilbert transfrom. and time-domain waveforms of analyzed measured ultrasonic signal propagation. Finally, ultrasonic signal propagation in the material is displayed by ultrasound imaging technology. The experimental results show that taking the ultrasonic signal Hilbert transform method can not only effectively extract the ultrasonic signal propagation at the defect, but also the shape, size and distribution of surface defects can be intuitive, efficiently detected by ultrasonic propagation imaging. Hence, the Hilbert-transform ultrasonic propagation imaging technology provides a method for quantitative detection of defects in manufacturing.