Tensile tests of plastically deformed specimens were performed in order to investigate the relation between variation of magnetic characteristics and residual plastic strain. Deformed stainless steel (SUS316L) and carbon steel (SS400) specimens were investigated by the method of Magnetic Adaptive Testing, measuring and evaluating series of minor magnetic hysteresis loops. Reliable correlation was found between magnetic parameters and residual strain of the specimens. Magnetic descriptors also depend on the orientation of magnetizing field with respect to the direction of elongation. Based on these results, Magnetic Adaptive Testing is suggested as a highly promising non-destructive method for monitoring plastic deformation in different types of steel.