The abnormal phenomenon that water temperature tidal phase ahead of water level in the wells of Qixian，Shanxi，has been studied． We first checked the instrument's time system， using water temperature and water level changes in response to some big earthquakes． Then we calculated the phase lags between water temperature and water level through harmonic analysis． The result shows that water temperature tidal phase ahead of water level is objective and this phenomenon exists in all the recording history． It also shows that the water temperature changes are caused by water level changes，since they have the same rhythm of phase lag variations over time． By surveying the observation conditions，the study reveals that the fact that water flow is not smooth in the wells is the reason for the abnormal phenomenon．