Abstract: To reconstruct the shape of elastical materials,according to the Born approximation solution of the scattering of three-dimensional elastic waves,the authors analyze the Born approximation solution of the two-dimensional scattering and discuss the scattering of the square void in long rod made of Al.Identification of flaw's geometrical character is given by two dimensional inverse Born approximation under the condition of low frequency,and simulated identification is performed for three square voids on computer.The simulated results show that two dimensional inverse Born approximation is an effective way for identification of the flaw.