Transformer winding deformation is one of the main types of transformer faults. To check if a power transformer is being under winding deformation, the transformer can be connected in a current transformer during its testing. A transformer winding simulating model is set up under this connecting manner. Then the simulation has been performed with current source which is the frequency sweep power. The simulation results show that the winding deformation can be reflected effectively with current source method. This method lays the foundation for the realization of on-line monitoring and diagnosis of the transformer neutral directly grounded side winding.