The AE(acousticemission) signals emitting from laser welding were sensed with an electrit condensermicrophone and analyzed with wavelet analysis to characterize their time-frequencydistributions. Based on the detail signals which were extracted from AE signals viawavelet analysis, a signal Intensity-Moving-Average(IMA) curve was defined in this paper.It was shown that the IMA curve of good-quality, full penetration welds was different fromthat of poor-quality welds, defined as either welds with misalignment problem or weldshaving a gap between the sheets being joined. According to the curve which shown to becapable of recognizing the transformation of welding states commendably, defects can bedetected quickly and exactly. With the help of IMA curve, it′s possible to realize the process control of laserwelding.