In this paper, the dependence of plastic deformation on nondestructive evaluation signals of nonlinear ECT (NECT) method is investigated through experiments. The test-pieces of SUS304 austenitic stainless steel are fabricated and tensile residual strains of different scales are applied to them by using a material testing machine. NECT signals of different exciting frequencies are measured, and the experimental results reveal that there are clear relationships between the plastic strains and the feature parameters of the NECT signals especially the loop area and the coercive force, which are sensitive to plastic strain at all tested excitation frequency. It can be concluded that NECT is feasible to quantitatively evaluate the plastic deformation in structures of the 304 austenitic stainless steel.