The direct and inverse scattering problems are a type of classical problem with symmetry. Numerical methods combined with machine learning are continuously being developed, and obtain good results in obstacle inversion problems. In this paper, we consider a crack shape with asymmetry; such problems are often ill-posed and nonlinear. Focusing on the inhomogeneous medium and limited-aperture far-field data, we propose a new sequence-to-sequence asymmetric convolutional neural network for recovering a crack via correlative far-field measurements. Taking the far-field data as the input and the shape parameters of a crack as the output, the features are quickly extracted using the convolutional and pooling layers. The Adam optimization algorithm is employed to update the weights and offsets of the neural network. Numerical experiments show that the proposed method can quickly and effectively reconstruct the shape of the crack.