Abstract: In order to solve the engineering problems,such as complex establishment of the multi-winding transformer model,long calculation time of composite short-circuit impedance and difficulties in calculation of the circulating current for parallel windings,a solution method for composite short-circuit impedance and circulating current in the parallel windings was proposed based on the equivalent single-turn inductance matrix and the equivalent circuit model of the transformer described by self-inductance and mutual inductance.In this method,all the short-circuit impedance between any two windings were computed by the equivalent single-turn inductance matrix.Combining the definition of composite short-circuit impedance with the ports’ conditions,all concerned composite short-circuit impedance and the circulating currents could be calculated only once through compiling the corresponding general calculation procedure in Matlab.Finally,taking a twelve-winding transformer as an example,the results calculated by the proposed new method were compared with the testing ones,which indicates that the calculation results of composite short-circuit impedance can meet the engineering requirements.