Considering the serious harmonic pollution of a 10 kV prefabricated substation, a novel technical scheme is proposed to integrate specific order filtering inductors into the distribution transformer, thus avoiding the large space occupied by an air-core reactor in the traditional passive filtering device or the excessive noise in an iron-core reactor. First, the decoupling technique of filtering inductors integrated into a transformer is analyzed. Then, based on the finite element simulation of an 800 kVA experimental prototype, the coupling matrix and inductance matrix of transformer winding are calculated by the reduced-order inductance matrix method, and the field-circuit coupling simulation of the system is carried out with the inductance matrix as interface. Finally, an experimental prototype was tested to verify the filtering effect. Simulation and experimental results show that the integrated filtering inductors distribution transformer had satisfying harmonic suppression and passive compensation. Moreover, the integrated filtering inductors had characteristics such as low decoupling with other windings, smaller occupied space and lower noise.