Abstract: Due to rough surface and thickness non-uniformity of forging pieces,manual ultrasonic testing has been commonly used in forging scanning system.As a result,low efficiency and poor quality are unavoidable for not being able to use the standard B-scan and C-scan imaging techniques.In this paper the ultrasonic testing methods of "depth-gray" imaging,which includes the path planning,full-wave sampling,signal processing,wave-form analysis and scanning imaging for flaw,is proposed,and thereafter illustrated with its promising effects in practical application.The approach is especially useful in promoting intelligence and automation of ultrasonic testing of aircraft forging and thereby improves the efficiency and reliability of testing.