The local meteoric water line (LMWL) is a significant benchmark in regional water cycle research. Because of the limited numbers of monitoring stations, most sites cannot obtain the LMWL easily, and could only refer the LMWL of the nearest monitoring station or the Global Meteoric Water Line (GMWL), or there needs a long term monitoring before analyzing and obtaining. There also exist many limitations in the conventional methods to obtain the LMWL. A case study was carried out in the Beijing Plain, and a new simple method of obtaining the LMWL was proposed in this paper. The data of the δD and δ18O of historical periods can be got through quaternary groundwater sampling and analysis, and the LMWL was obtained with the data directly. Compared with the LMWL equations using the conventional method, the new method is shown to have many advantages. The method could save a lot of human and physical resources and monitoring time, is relatively simple and is more practical. Moreover, it has a better fitting effect. It is also noted that the method has some deficiencies: it requires the sampling sites to be selected from an alluvial plain area with fine deposition particles.