Fast and accurate fault location for transmission lines plays an important role in safe and steady run of power system .The conventional single-terminal method of fault location can not eliminate the influence of the fault resistance and remote in-feed, two-terminal methods commonly based on phase calculation in frequency-domain. This paper presents a time-domain fault location algorithm based on modal theory and synchronized sampling at two ends. The algorithm needs less data from another end and is not influenced by the following factors, such as fault resistance, operation state, fault type, etc. The algorithm can also be used in fault location for double-circuit line. Lots of simulation results using EMTP have proved the high accuracy of the method.