Abstract: The basic idea of marching-on-in-frequency method is that the discretized integral equation is solved by using one of the iterative approaches, and the initial estimates are produced by using an extrapolation scheme based on error minimization. The iteration formula in the CST is corrected, which increases the convergence rate considerably at lower frequencies. It is important for convergence that the iteration is carried out in complex-frequency domain, because the matrix condition is improved and more accurate initial estimate can be obtained from the stner othly varying solutions in complex-frequency domain.