This paper describes the assessment method of deterioration condition for a power transformer using SFRA. Frequency Response Analysis(FRA) is a method to evaluate the mechanical and geometrical integrity of the core and windings within a power transformer by measuring the electrical transfer functions over a wide frequency range. SFRA is sweep frequency response analyzer for power transformer winding diagnosis. The FRA is a comparative method, that evaluates the transformer condition by comparing the obtained set of FRA results to reference results on the same, or a similar, unit. FRA techniques were widely used and much more sensitive than the traditional and internationally accepted method of impedance measurements, but that work was required on standardization and interpretation. In order to analyze the deterioration condition for power transformer, overvoltage test and mechanical distortion test were carried out. The deterioration condition for power transformer was evaluated by SFRA. It is intended to present the elemental technology of assessment method for power transformer using SFRA.