Abstract: Described in the article is a modified sinking EDM sampling machine which is mainly used to make NDT reference pipes.Discussed here are the main aspects of the said machine, including its operating principle, sampling effectiveness, working conditions as required, operation procedures, and the cutting technique for timely measuring the flat bottom hole technical status, etc.The modified sinking EDM sampling machine is capable of making small diameter, great depth standard artificial notches on steel pipe inner surface so as to get the NDT reference pipe type category enlarged.