In this paper, we propose a 2-step frequency-domain channel estimation scheme suitable for training sequence inserted single-carrier (TS-SC) block transmission using frequency-domain equalization (FDE). In the first step, the received training sequence having cyclic property is constructed for frequency-domain channel estimation to obtain the instantaneous channel estimate. Improved channel estimate is obtained by simply averaging the instantaneous channel estimates over several blocks. In the second step, the maximum likelihood channel estimation is carried out iteratively by using both the estimated symbol sequence and the training sequence. The BER performance with the proposed frequency-domain channel estimation scheme is evaluated by computer simulation. It is shown that the proposed channel estimation scheme achieves a BER performance close to the perfect channel estimation.