Abstract: The traditional derivative-based traveling wave protection method has the problem of operation failure when the high impedance faults occur. Based on the analysis of the influence factors of the fault traveling wave, this paper draws the conclusion that the distortion of fault traveling wave is related to the fault distance, and the amplitude of fault traveling wave is related to fault impedance. A basic fitting function was proposed to fit the zero-mode fault current, and the parameters reflecting fault distance and impedance were obtained. The fault impedance estimation interval can be obtained by extracting fault information from the obtained parameters, and the adaptive non-unit traveling wave protection method was realized. The simulation results show that the proposed method can protect the DC transmission line fast and effectively, even with high fault impedance. Comparing with the traditional traveling wave protection and transient-based protection, the proposed method has higher sensitivity and can protect wider area of the DC transmission lines.