Abstract: At least three times of eddy current tests are required during the manufacture of 690 Ni-base alloy heat transfer tubes used in nuclear power plant steam generator. The initial eddy current test is mainly to detect the outer surface defects of the heat transfer tube in the case of straight pipe, and the second time one takes place before bending the tube and employs the inner pass-through probe to control the SNR of the heat transfer tube inner eddy current signals. The final one takes place after bending the tube and is mainly to detect the inner wall defects of the heat transfer tube by inner pass-through eddy current probe. This paper introduces the opportunity, purpose, parameter setting, signal analysis and acceptance evaluation of three eddy current tests. In addition, the effect of integral stress relief heat treatment on eddy current test is studied by experimental comparison. The results show that the integral stress relief heat treatment has no effect on the inner eddy current signal of U-shaped heat transfer tubes.