Abstract: This article described the functions of Eddy Current tubing reference specimens. The difference of two type artificial discontinuities (drilled hole and notch) was shown through a contrast experiment, and it was proven that notch discontinuities were better than drilled hole discontinuities during ET operation because the ET phase angle signal due to the former discontinuities was more similar with tube outside surface discontinuities. Now that drilled hole is used by many tube manufacturers, it is therefore suggested that the tubing reference specimens may be processed as two type artificial discontinuities(drilled hole and notch) in order to compare the phase signal of drilled hole and notch and enhance testing quality.