A DHT-based frequency-domain equalizer (FEQ) is presented to eliminate the real-to-complex transformation (R2CT) for the discrete Hartley transform (DHT) based discrete multi-tone (DMT) systems. The DHT-based FEQ can be further used to develop the DHT-based per-tone equalization for DMT systems. In this paper, the DHT-based DMT ADSL system is adopted as a vehicle to demonstrate the DHT-based FEQ performance. Based on the steepest descent (SD) algorithm, the DHT-based FEQ is derived without employing R2CT, which costs 2N-addition. N is the number of DHT points. The performance analysis of the DHT-based FEQ proves no signal-to-noise ratio (SNR) loss compared with the DFT-based FEQ, and the bit allocation and data rate are identical with the performance analysis.