According to a survey conducted by the National Aeronautics and Space Administration, many non-destructive testing methods are considered to be divided into six categories and about 70 kinds. However, the following are common in practical applications:

Conventional non-destructive testing methods are:

　　－ Ultrasonic Testing（ UT）；

　　－Radiographic Testing（RT）；

　　－Magnetic particle Testing（MT）；

　　－Penetrant Testing ( PT）；

　　－Eddy current Testing（ET）；

Unconventional non-destructive testing techniques are:

－Acoustic Emission(AE)；

　　－Leak Testing（UT）；

　　－Optical Holography；

　　－Infrared Thermography；

　　－Microwave Testing