Abstract: In this paper, the long time series of well water-level data of 12 wells in Sichuan and Yunnan area are analyzed by the tidal analysis software of Baytap-G, and well water level tidal response characteristic parameters (amplitude ratio and phases) are extracted . We analyzed the features of shape and stage change, and characteristic parameters of the tidal response of well water level before and after earthquakes, which can provide a new method and approach to analyze the response relationships between well water level and earth tide and barometric pressure. The results show that Luguhu well and other 9 wells are affected by earth tides, and their well water level amplitude ratios and phases are relatively stable; Nanxi Well and Dayao Well water level changes are affected by the barometric pressure combined with tide force, their well water level amplitude ratios and phases are more discrete. The water level amplitude ratios and phases of Jiangyou Well, Luguhu Well and Dongchuan Well are significant to large earthquakes, the relationship between the seismic energy density and the water level amplitude ratios and phases of M 2 wave of the three wells are presented.

Key words: Well water level, Barometric pressure, Earth tide, Amplitude ratios