Abstract: In this paper a new image processing method was developed to determine the in plane vibration amplitude of a harmonically oscillating object from its two images. These images were captured with a CCD camera, the first image was recorded when the object was in static state and the second image was a time-average image recorded when the body was in vibration. An iterative algorithm based upon digital-image correlation was also presented to solve thederived nonlinear equations.In order to get a higher accuracy a bilinear interpolation was used totransform the original discrete images into continuous images. Experimental results show that the method can be used to determine amplitudes of harmonic vibrations with reasonable accuracy.Besides, this method has trivial requests for picturing equipments and experimental environmentand is especially suitable for field measurement.