The brazing quality of aluminum alloy brazed water-cooled plate is very important to the safe and stable operation of the cooling system.In order to effectively detect the brazing defects of water-cooled plate,this paper determines the ultrasonic C-scan technology based on test sample,and carries out ultrason-ic C-scan on the water-cooled plate produced by enterprises,and analyzes the calculation of brazing rate and common brazing defects of water-cooled plate.The results show that the scanning sensitivity of aluminum alloy brazed water-cooled plate can be determined according to the actual workpiece being tested.There is a one-to-one correspondence between the position of the artificial defect obtained by ultrasonic C-scan and the position of the test specimen.Ultrasonic C-scanning technology can directly reflect the welding gap and flow channel blockage.