Abstract: The three-dimensional triangular roll iron core transformer has an iron core structure composed of three independent core frames spliced in pairs. The iron core structure of this new structure is quite different from the conventional three-phase planar laminated core structure, which affects the magnetic field distribution of the transformer. In this paper, the magnetic field distribution law of this three-dimensional triangular structure iron core is analyzed and studied, and the magnetic field distribution law of this structural iron core is verified by finite element simulation.