Aiming at identifying the shape of arbitrary object quickly and accurately, cucumber was taken as a research object. The boundary of cucumber image was extracted through digital image processing including image enhancing, threshold processing, morphological operations and edge extraction operation. Then elliptic Fourier descriptors were used to describe the boundary information of cucumber quantitatively, and the elliptic Fourier descriptors were normalized at start point，rotation and size after that. The cucumber shape was reconstructed by using different numbers of harmonics of elliptic Fourier descriptors with error analysis. The experiment results showed that the complex shape of cucumber could be described by a small amount of elliptic Fourier descriptor through the description of elliptic Fourier method, and the elliptic Fourier descriptor could reconstruct the original shape accurately.