Railway lines are long, and the full coverage of line monitoring sensors faces the problem of huge cost. In this paper, the research on the optimization method of railway line monitoring sensor layout is carried out to address this problem. Firstly, based on the perception accuracy of the monitoring sensor algorithm to the abnormal event, the calculation method of monitoring sensor layout distance is proposed. Then, based on the method, monitoring sensor layout methods for the conventional area, the key area and the interface area are proposed. Finally, a case study is carried out on the design line. The calculation results show that compared with the existing standards, the method proposed in this paper can effectively reduce the cost of monitoring sensor layout while maintaining high perception accuracy. This method is more economical and reasonable.