Abstract: Under dense multipath channels, a practical UWB ranging system usually adopts TOA-based energy detection receiver. The accuracy of TOA estimation determines the accuracy of ranging. Threshold comparison is used a lot in ED and the designing of threshold affects the accuracy of TOA estimation greatly. In this paper, we apply the maximum probability of detection method to the energy-based TOA estimators. By improving the method of calculating the probability of detection, a new criteria to determine the threshold value and detect the DP is proposed. The algorithm calculates the probability of detection of DP during searching the optimal threshold. The DP is determined when the difference of the DP detection probability reaches maximum. And then the optimal threshold is also acquired. The paper analyzes theoretically and presents the novel procedure of the proposed TOA estimation method. In the Simulation, we compare our method with other methods. Simulation results show that our method outperforms others and verify the effectiveness of our method.