This paper describes the dispersion characteristics of first-period P waves recorded by seismic stations near Datong window by measuring the medium quality factor (Q_m) and analyzing Q_m variations before and after the occurrence of earthquakes near and far from Datong window. By applying this method to the SZZ record of the Datong window earthquake sequence from 2001, we obtained the following results: before 3 earthquakes near the Datong window and 6 earthquakes far from the Datong window, the Q_m was the high values over 1 times mean square error; but Q_m returned gradually the background after these earthquakes. However, after eliminating the influences of epicentral distance and depth, large anomalies were still observed and small anomalies disappeared before the earthquakes. Furthermore, the corresponding rate of earthquake decreased from 0.9 to 0.5. Compared with the frequency of Datong window, the Q_m could better reflect earthquake probability. The results of YAY showed that before 1 earthquake near the Datong window and 2 earthquakes far from the Datong window, the Q_m were the high values over 1 times mean square error, and false and omitted cases were observed. Minimal changes to the curve were observed after eliminating the influences of epicentral distance and depth. Preliminary analysis suggested that the short-term high-value anomalies of Q_m before earthquakes recorded by the SZZ and YAY stations could directly reflect the seismogenic process. However, the Q_m recorded by the two stations obviously different before the same earthquakes. Two reasons may explain this phenomenon. The small earthquakes measured by Q_m differed between the two stations as these stations were located in different geological and tectonic positions. The SZZ station was located inside the Datong basin, while the YAY station was located in its eastern border. This difference could lead to the different deep medium and broken medium through by seismic wave ray paths and, therefore, marked variations in Q_m values. The length and width of Datong window were 60 and 5 km, respectively, so high-value anomalies were limited in this area. From the results of Q_m, for the moderate earthquakes which are not only near the Datong window but also far form Datong window, the amplitude of anomaly was almost the same and the distribute range had little change. As such, determining the variation of deep anomalies near or far from Datong window by using the spatial anomaly distribution is difficult. The Datong window showed high-value anomalies before the far-field earthquake of the Shanxi seismic belt because this window is located to the north of the same continental rift. However, the reason why it had high-value anomalies before the earthquakes of Zhangjiakou-Bohai seismic belt which were a few hundred kilometers away, it was possible that the "Y" type of low wave velocity anomaly from Datong volcanoes to below Bohai had played an important role in transmission.