The zero-sequence impedance or impedances of the transformers is an important basis for the selection and setting value calculation of relay protection components, and is an important parameter of power systems. It can be used to accurately calculate the zero-sequence component of short-circuit current in power system accident states. The zero-sequence impedance of transformers is mainly affected by the structure of the iron core and the connection group of the windings. Analytical methods are difficult to accurately calculate the zero-sequence impedance, while finite element methods can better solve this problem. Taking YNyn0d11 3-phase 3-leg transformer as the research object, a finite element field circuit coupling calculation model for zero-sequence impedance is established in Ansys Maxwell, and three calculation methods for zero sequence impedance are studied: energy method, volt-ampere method, and inductance matrix method. Based on the above model, the influence of fuel tank and magnetic shielding modeling methods on the accuracy of zero sequence impedance calculation is studied. The error between the calculation results and the transformer test data is within 5%, which meets the engineering calculation accuracy requirements and verifies the effectiveness of the three proposed calculation methods.