Abstract: Inverse theory and regularization method are used to the current inversion imaging of nugget cross-section. The inversion image can be used to evaluate spot weld intuitively, which meets to the requirements of higher weld quality. Firstly, the forward model which describes the relationship between the current distributions of nugget cross-section and magnetic field was established, and its reliability was verified by experiments. Secondly, the inversion model was established and the numerical experiments were conducted to verify correctness of the inversion model. In the end, different current values were chosen for the resistance spot welding experiments, and then the collected magnetic signals were transformed into current signals, which were displayed in the form of image. Experiment results show that the inversion image can describe the characteristics of nugget cross-section current distribution and reflect the quality of nugget, but regularization parameters impact the accuracy of inversion image which will remove from the real one if the parameter is too large or small.