Abstract: By comparatively analyzing the diurnal variation of geomagnetic elements of several groups of adjacent geomagnetic stations in the West, Southwest and East of China, it is found that the diurnal variations of geomagnetic elements at each station are spatial differences. The characteristics of the difference are that they have the same change trend but not the same amplitude. Combined with some examples, field observation raw materials are analyzed. When the geomagnetic elements of adjacent geomagnetic stations are used for generalizing, there are different results, and these differences are closely related to the time and season of observation. In the examples of this article, the differences of generalized results of magnetic declination (D), horizontal magnetic field vector (H), vertical magnetic component (Z), and geomagnetic total intensity (F) are generally 0.5′, 6 nT, 4 nT, and 6 nT; and such difference values may affect the earthquake situation assessment. Therefore, continuous observation at fixed points is very important in the geomagnetic monitoring of earthquake, and the mobile geomagnetic observation should just be used as a supplement and auxiliary means.