The work presents the influence of the low voltage pulsed magnetic field (LVPMF) on the microstructure transition of superalloy K4169. A gradient microstructure sample of superalloy K4169 with columnar-grained, coarse-grained, and fine-grained is prepared by combining the LVPMF with directional solidification, which provides a new method for the gradient microstructure preparation for the superalloy. The distribution of the Lorentz force and flow field under the LVPMF are simulated to reveal the microstructure transition mechanism. It is considered that the microstructure transition should be attributed to the coupling effects of the Lorentz force and forced convection.