Abstract: In this paper, characteristics and differences of ultrasonic signals generated by point light source and line light source are mainly studied under condition of maintaining the same laser pulse energy and the same detection position through established laser ultrasonic testing platform. Amplitude of ultrasonic signal and waveform of ultrasonic signal generated by point light source and line light source are studied at different detection positions. It is found that amplitude of ultrasonic signal is increased from 1.3 V to 1.7 V, which increased by 0.4 V after point light source is replaced by a line source in the same detection position. When detection position is gradually increased, attenuation amplitude of ultrasonic signal amplitude excited by point light source is 75.78%, while attenuation amplitude of ultrasonic signal amplitude excited by line light source is 34.92%. Results show that under the same power density, ultrasonic signal produced by line light source is increased by 40.86% of ultrasonic signal amplitude generated by point light source, resulting in strong surface wave and better signal to noise ratio.