There is a serious deviation of transformer short － circuit impedance after the short － circuit endurance test of transformer No． 2 in a 110 kV substation． In order to accurately judge the state of the test transformer and find out the reasons for the unqualified test，a winding deformation analysis method———Cx － Xk (% )based on winding capacitance and short － circuit impedance test is proposed through the mathematical model analysis of transformer winding capacitance and short － circuit impedance，which provides a basis for transformer repairing． With only single impedance test data，the deformed winding is analyzed in combination with the change of winding capacitance． The results of decomposition inspection of transformer which is returned to factory verify the feasibility and correctness of the proposed analysis method，which provides an effective analysis method for the analysis of transformer test results．