In this paper，the authors analyze the daily ranges of vertical about 76 geomagnetic stations from January 1，2008 to December 31，2010. They use those data to study the spatial and temporal characteristics of Z ranges and the results are summarized as follows: ① In temporal， they adopt the regressive analysis and FFT analysis to analyze the data，the results show that the Z component daily ranges of all stations have an cyclical variation obviously． The computed Fourier spectra of all the data sets have clearly resolved the required periodicities in the data，in the form of distinct peaks at 365-，183-，122-，and 73-day periods． The power spectral of 365-day is the highest in all periods． ② In spatial，the daily ranges show nonlinear variation with latitude in China． The results show there exists a point of inflexion ( maximal value point) nearby about 25°N． The daily ranges of Z rise during 15°～25°N and have a good linear decrease variation along with 25°～50°N． ③ Comparing the variation of Z daily ranges with the Sq current inversion in spatial and temporal，they find that the Sq current system causes the spatial and temporal characteristics of Z ranges． ④ If the latitudes of the maximum amplitudes of variation of the vertical component on geomagnetic quiet days are roughly taken as the latitudes corresponding to the foci of Sq overhead current system，you can see that these latitudes of foci become higher in summer，lowest in winter and highest during Equinoxes，displaying conspicuously monthly and daily variations． For two successive geomagnetic quiet days，the latitudes of foci may vary ten degrees．