The invention discloses a power distribution network neutral line zero sequence harmonic suppression device with a changed iron core structure. The device comprises a zero-sequence filter, the zero-sequence filter comprises four core columns and six windings, the winding numbers of the windings are same, the core columns are parallel to one another, the included angle between a first parallel plane and a second parallel plane, the included angle between the first parallel plane and a third parallel plane and the included angle between the second parallel plane and the third parallel plane are all 120 degrees, the first parallel plane is composed of the first core column and the second core column, the second parallel plane is composed of the first core column and the third core column, the third parallel plane is composed of the first core column and the fourth core column, three windings are wound around the first core column, and the other core columns are each provided with one winding in a winding mode; each winding phase is divided into two half windings which are located on two different core columns respectively, each phase of voltage is obtained by reversely connecting the two half windings located on the different core columns, the leading-out ends of three lower half windings are in short connection with one another and then are connected to a power grid neutral line, and three upper half windings are directly connected with a three-phase power grid in parallel. Accordingly, a low-resistance channel is provided for zero-sequence harmonic currents of a power distribution network, and then the zero-sequence harmonic currents in the power distribution network neutral line are filtered out.