To overcome the limitation of previous feedback frequency synchronizers, which can only be applied to track small carrier frequency offset (CFO) in a fraction of the subchannel spacing, a blind CFO detector with large acquisition range is proposed in this paper. Based on the characteristics of CFO-induced complex weighting factors, a novel cost function of CFO is developed, and frequency synchronization is accomplished through the maximization of this cost function. To simplify the implementation of the proposed method, a low-complexity adaptive algorithm is introduced, which simply utilizes the FFT operation of the OFDM demodulator to generate the error signal for each iteration. Both analytical and computer simulation results are presented to demonstrate the performance of the proposed method.