The stress states of ferromagnetic coatings in the electroplating process have a great influence on the performance of electroplated products. In this paper, aiming at the stress detection of electroplated nickel coatings with micron-level thickness, a magnetic incremental permeability technology has been proposed to perform non-destructive testing of tensile stress in nickel coatings (with thickness on the micrometer scale) on the surface of metal components. Firstly, an experimental device was developed to synchronously measure the uniaxial tension, strain, and magnetic incremental permeability signals of electroplated nickel coating, and conduct the magnetic incremental permeability detection experiments. Secondly, the influence of tensile stress on the incremental permeability butterfly curve was qualitatively analyzed, and two characteristic magnetic parameters sensitive to tensile stress in nickel coating were selected from the experimental signals. Finally, the characterization ability of magnetic parameters on the tensile stress of electroplated nickel specimens was quantitatively analyzed based on the quadratic function. Experimental results indicated that the two selected characteristic magnetic parameters based on the magnetic incremental permeability exhibited a parabolic dependency relationship with tensile stress (goodness of fit was greater than 0.95), the established equation was used to quantitatively predict the tensile stress of nickel coatings, and the results showed that magnetic incremental permeability technology can achieve the quantitative detection of elastic tensile stress on ferromagnetic nickel coatings with the thinnest thickness of 2.809 μm.