Abstract: To recover the 3D scene,a 3D reconstruction algorithm based on ID subspace is presented under orthographic projection.It relies on the facts that the rows composed of all the image points span the same linear subspace as the rows composed of the 3D space points and that the basis of the subspace can consist of the two rows composed of the first image points and a row vector which is orthogonal to the former.The row vector is obtained,and lastly the 3D reconstruction is accomplished.The experiments with both simulation and real data show that the algorithm is robust and has small reprojection errors.