Abstract: Aiming at the inaccurate problem of the routine line protection fault location when the line together with 750 kV series reactor trips,systematically introduces the principle of single and double side protection fault location,deeply analyzes the effect of series reactor on protection fault location,and the anomaly is reproduced by example analysis and data calculation.It is verified the appreciable error between the results of protection fault location and the actual distance when the line together with series reactor trips,and the results of protection fault location do not have reference.It puts forward a series of effective improvement measures to optimize the line fault location with series reactor.it can provide the reference of the design and debugging,operation and maintenance for the line fault location with series reactor in the follow-up substation.