Digital television/terrestrial multimedia broadcasting (DTMB), announced as the Chinese digital television terrestrial broadcasting (DTTB) standard, uses pseudo-noise (PN) sequence as guard interval (GI) and the training sequence for both multi- and single-carrier block transmissions. The conventional channel estimation methods can be performed through either the subtraction of the PN sequence or the cancellation of residual inter-symbol interference (ISI). In this paper, a novel iterative method is introduced to estimate the overlapping part of PN sequence, meanwhile the channel impulse response (CIR) estimation can be obtained and updated via the reconstruction of the PN sequence in an iterative manner. Simulations show that the proposed algorithm can effectively reduce the ISI and improve the symbol error rata (SER) of DTMB system over slowvarying broadcasting multipath channel even with long delay spread. In practice, the proposed algorithm can be applied to the DTMB receiver-chip directly with low-complexity cost.