By applying a periodic pulsed current, the minor hysteresis curves of ferromagnetic material are measured. Because the minor hysteresis curve obtained has the characteristics of multiple values, the traditional solving method of nonlinear equations can't be directly applied. So considering a piecewise method, the multi-value minor hysteresis curve is converted to a series of single-value nonlinear curves according to the turning points, and then uses the solving method of nonlinear equations to solve every single-value curve. The paper uses finite element software for simulation to obtain the pulsed eddy current field distribution of a ferromagnetic pipeline and the transient induced voltage curve of pick-up coil. The experimental results show that the simulation results are effective. In the case of a constant pipeline outer radius, the wall thickness is changed, and the curves of the relative change of the transient induced voltage with pipelines and without pipelines are obtained. Then effective characteristics are extracted, the mathematical expressions are established between wall thickness and characteristics. The final experimental results which document the accuracy of the mathematical expressions can be used to detect the pipeline wall thickness. At the same time, it is proved that the characteristics extracted can effectively reflect the change of pipeline wall thickness.