Abstract: The distinctive acoustic signal emitted by plasma while laser welding diamond saw is regarded as a signal which is produced when a carrier wave with frequency of 16kHz is modulated with a periodical signal with frequency of 300Hz.A method to obtain the diagnostic signal, the acoustic feedback control system and the principle of laser welding diamond saw are described in the paper.Experimental results prove that in terms of welding qualities, acoustic feedback method is better than ordinary laser welding method.