The paper studies Sacks volume strains with the same well water-level observation data of digital minute values at Laishui stations in the Capital Circle Region． It is found that both tidal curve in thunderstorm periods have simultaneously significant distortion abnormal． The analyses of wavelet，regression and power spectral in comparison with the pressure data confirm that this was an interference due to a pressure instantaneous mutation triggered by thunderstorms． The value is about 8 times and 11 times higher than the background value． This phenomenon mainly occurs in the thunderstorm season from June to August． It also studies the laws and mechanisms of the cycle pressure wave affection on the volume strain and well water level． The coefficient curves between thunderstorm days and non-thunderstorm days are compared in terms of air pressure on the volume strain and well water level and their variations and features are summarized．