Abstract: In general, recognizable diurnal variation waveforms appear at 70 percent of the more than one hundred geoelectric field stations in Chinese mainland. In this paper, we discussed seven stations including Hai'an, Pingliang, Guazhou, which are representatively characterized by the electromagnetic environment, device system and the diurnal waveforms. Based on the tidal mechanism and the model of rock crack water seepage or the electric charges movement in crack water, and with the application of fast Fourier transform algorithm and vector analysis methods, we studied the phase correlation and influence factors of diurnal waveforms of the seven stations in multiple periods and multi-orientation during 2009—2015, and received the following conclusions: geoelectric field diurnal waveforms observed in each orientation always show the same or opposite phase correlation; the dominant orientation of rock crack will decide phase correlations among geoelectric field diurnal waveforms observed from multi-orientation when the connection mode between electrodes and the instrument is determined, and the correlations are relatively steady.