In order to solve the problem that traditional HVDC transmission lines have high requirements on communication channels when they rely on high-precision synchronous pairs, a two-terminal location method was proposed to calculate the fault distance by using the transmission time difference between fault traveling wave line mode and zero mode component in the line. The method extracted the transient information of the two modal components of the fault traveling wave,detected the moment when the two modal components arrived at the two ends of the line, and used the time difference between them to achieve fault location,overcoming the error caused by the unsynchronized clocks of the detection devices at both ends. For the problem that it was difficult to determine the wave speed of line-mode and zero-mode,the wave speed curve was fitted by mathematical methods combined with simulation data,and then the line wave speed and fault distance were continuously optimized through multiple iterations. Finally, more accurate values of the traveling mode wave speed and fault distance were obtained. A system simulation model was built in the PSCAD/EMTDC simulation platform to simulate the short-circuit condition of transmission lines under the condition of time asynchronism, different fault distances,and transition resistance. Through analysis and simulation, the results show that the method has high positioning accuracy, strong resistance to transition resistance, and good stability without the influence of time asynchronism.