In order to improve the efficiency and accuracy of the inversion of perfectly electric conductors (PECs), an iterative method based on linear approximation (IMLA) is proposed in this work. In the iteration, the computational complexity of the proposed IMLA is well reduced by the implementation of a linear approximation, which makes the inversion highly efficient. Although the linear approximation is employed to solve the inverse scattering problem (ISP), the full-wave effect is still considered to improve the inversion accuracy in the iteration. In addition, to effectively solve the ill-posed ISP and improve the inversion quality, Tikhonov regularization method is introduced, and the corresponding regularization parameter is determined by a self-adaptive L-curve method. To verify the effects of scatterer size and noise on the reconstruction, typical 2-D experiments are given, and the results show that the proposed IMLA could efficiently and accurately retrieve complex PEC scatterer shapes, even in the presence of noise.