The invention provides parameter determination and modeling methods of a coupling unit of an AC/DC transformation circuit. Equivalent inductance of an input end of the coupling unit is acquired when at least one phase of primary winding of the input end of the coupling unit is in an independent state and at least one phase of secondary winding of an output end of the coupling unit is in a state ofan open circuit after parallel connection; and phase-dividing calculation is carried out for equivalent inductance of the output end of the coupling unit according to the equivalent inductance of theinput end of the coupling unit when at least one phase of the primary winding of the input end of the coupling unit is in a parallel connection state and at least one phase of the secondary winding of the output end of the coupling unit is in a state of a short circuit after parallel connection. Therefore, according to the methods, parameters of the coupling unit in the AC/DC transformation circuit can be obtained, and an emulation model which can simulate electrical characteristics of a coupling transformer can be established, and problems of a large covered area and a high manufacture costof a DC-side capacitor of a power electronics transformer can be further solved through the emulation model.