Eddy current testing is one of the most extensively used methods for defect detection. In eddy current testing, the trajectory of the impedance data when scanning a crack is presented as a Lissajous curve (LC) in the complex plane. This paper has proposed a novel analytical model for describing a LC. Further, a new feature extraction method is implemented which automatically compute four geometric features (amplitude, width, angle and symmetry) from Lissajous figures. In addition, some experiments are conducted to verify the proposed method.