Abstract: Aluminum alloy storage tank is widely used in transportation and storage of liquefied natural gas. The ultra-low temperature storage condition of liquefied natural gas has put forward special requirements for the manufacturing quality of storage tanks. This paper mainly introduces the application of phased array ultrasonic testing in aluminum alloy LNG tank. The results show that the detection of butt weld of aluminum alloy LNG storage tank by phased array technology can completely meet the requirements of the standard, and the imaging is intuitive, and the defect can be scanned at multiple angles at one time, and the detection rate of the defect is high, which has obvious application advantages.