A corrosion resistant CuNi cladding was deposited on SM45C (equivalent to AlSl1045) substrate by DC inverse arcwelding. During the welding process, a three channel acoustic emission (AE) monitoring system was applied to detectthe crack signals generating from both the cladding process and after cladding. Characteristics of the welding cracksignal and noise signal had been analyzed systematically Based on the record time of the signal, the solidificationcrack and delayed crack were distinguished. By two-dimensional AE source location, the crack position was located,and then investigated by scanning electron microscopy (SEM). Results showed that the AE system could detect thewelding crack with high sensitivity and the two-dimensional source location could accurately determine the crackposition. Microstructures of the cladding and heat affected zone (HAZ) were examined. Dendrites in the claddingand coarse grains in the HAZ were found. A corrosion resistant CuNi cladding was deposited on SM45C (equivalent to AlSl 1045) substrate by DC inverse arc welding. During the welding process, a three channel acoustic emission (AE) monitoring system was applied to detect the crack signals generated from both the cladding process and after cladding Characteristics of the welding cracksignal and noise signal had been analyzed systematically Based on the record time of the signal, the solidificationcrack and delayed crack were distinguished. By two-dimensional AE source location, the crack position was located, and then investigated by scanning electron microscopy (SEM). Results showed that the AE system could detect the welding crack with high sensitivity and the two-dimensional source location could accurately determine the crack position. Microstructures of the cladding and heat affected zone (HAZ) were examined. Dendrites in the cladding and coarse grains in the HAZ were found.