The laser ultrasound detecting technology has many advantages of noncontact, quick and high efficiency. It has good application foreground in the field of nondestructive detection of carbon fiber composite materials. In this paper, the theory of laser thermoelastically generated ultrasound stress is studied. A noncontact scanning laser ultrasound detecting system is set up for the realtime and online detection of the structure health status of the carbon fiber composite materials. The relationships among the ultrasound signals and laser parameters and receiving distance are experimentally studied. The results show that the laser ultrasound detecting technology can be used for the structure health detecting of carbon fiber composite materials effectively. The laser ultrasound detecting system adopts the scanning laser technology. Its single detection only needs 0.1 s, thus the detecting efficiency has been improved. The system is simple in structure, easy to operate and easy to install and debug. The ultrasound signals amplitude increases with the increase of laser energy and reduces with the increase of receiving distance in thermoelastical range.