Aiming at the low SNR of laser ultrasonic signal,data acquisition and processing system based on digital average and wavelet analysis are designed by analyzing the characteristics of interference noise.By using synchronized trigger technology,laser ultrasonic signal are collected at regular intervals,and then all the sampled signals are summed and averaged.Eventually,appropriate wavelet base,decomposition level and the threshold method are determined,and wavelet de-noising is further performed for the signals after digital averaging.The experimental results show that this method can efficiently remove noise,and improve the signal noise ratio of laser ultrasonic signal.