Abstract: We studied the geoelectric field daily variation in the quiet day of the solar activity (called as “the geoelectric daily variation” for short) by use of the minute-value data of 12, 194 days from 21 geoelectric field observatories in the range of 98°13′~126°35′E and 30°30′~44°52′N of the mainland of China, the data were recorded by 6 measuring channels at every observatory, and aquired some understandings for the time and spatial regularities of variation and the reason causing the regularities. We obtained the following two new results:① the amplitude of the daily variation obviously decreases when the geographical latitude get higher, and besides, it is related to the underground electric property structure of the observatory; ② The seasonal change of the amplitude approximately accords with the Loyd season in the astronomy that the amplitude is maximal in the J-season, minimal in the D-season, and intermediate in the E-season, which is well in concordance with the changes of the total current intensity of the current vortex field in the middle latitude area of the earth with the three Loyd seasons.

Key words: Geoelectric field, Quiet day of the solar activity, Variation, Amplitude, Period, Frequency spectrum