Abstract: In the non-destructive testing of light hydrocarbon unloading buffer tank welds, the conventional ultrasonic testing can not accurately analyze the defects, so the ultrasonic imaging method (ultrasonic phased array detection method and ultrasonic time-of-flight diffraction) is used to the welds of the buffer tank welds. The results show that the two methods can make accurate judgments on the character and size of the defects and eliminate potential hazards to safety.