Abstract: This paper utilized data acquired from the dense magnetometer array established as part of the National Key Research and Development Program project titled “Development of new portable seismic monitoring devices” in the southern segment of the Xiaojiang fault zone (Yuxi and Honghe regions of southern Yunnan). Employing the Empirical Mode Decomposition (EMD) method, a quality analysis was performed on the Z-component data outputs. The results indicate that the standard deviation of the synchronous differences in diurnal variations of the geomagnetic Z-component across various stations stabilizes within the range of 0.86 nT to 1.17 nT, with correlation coefficients for magnetically quiet days achieving notably high values between 0.9720 and 1. This highlights favorable consistency in the diurnal variation patterns, amplitudes, and conditions during quiet days. The outcomes of this study contribute significant insights into the temporal and spatial characteristics of geomagnetic field variations in the region, offering valuable references for comprehending local geophysical phenomena and potential seismic activities.