An embodiment of the invention relates to a method of determining transformer winding amplitude deformation. The transformer winding comprises an external winding, a middle winding, and an internal winding. The method comprises steps of: with every two of the external winding, the middle winding and the internal winding as a winding pair, determining ground capacities of two windings of each winding pair; according to the ground capacities of two windings of each winding pair, determining rates of change of the ground capacities of the two windings of each winding pair; according to the ratesof change of the ground capacities of the two windings of each winding pair, determining whether the middle winding and the internal winding deform in amplitude; and if the middle winding and the internal winding deform in amplitude, determining deformation degree in amplitude according to the rates of change of the capacities. According to the two-step analysis method, whether the windings deformin amplitude is determined according to the rates of change of the capacities, then deformation degree is determined by measuring the rates of change of the capacities. The method is easy to conductand is highly accurate.