The short-circuit impedances of multi-winding transformers vary in different short-circuit states, which are called composite short-circuit impedances. With different short-circuit states, the circulating currents of the windings are different. It takes a long time to solve the composite short-circuit impedance and the circulating current, and there are some difficulties in solving the formulas of the transformer. Aiming at the problems above, a new calculation based on a new field-circuit coupling method was provided. By building the simplified magnetic field model, the inductance matrix of all the transformer windings was obtained. The external circuit and the inductance matrix were combined, and the composite short-circuit impedances and the circulating currents of the multi-winding transformer can be obtained quickly. Taking a 8-winding transformer for instance, the measurement results show that this new calculation method is of high accuracy, low consuming time and high engineering value.