Abstract: The bacterial community structures and hydrogeochemical parameters in aseismic times provide the backdrop for illustrating the response of bacterial community to moderate and strong earthquakes. Water samples were collected from December 2010 to April 2011, during which period two felt earthquakes of MS3.1 and MS3.6 successively occurred near Urumqi. A terminal restriction fragment length polymorphism (T-RFLP) technique was used to analyze the bacterial community structures, diversity, stability and variations of the dominant groups and peculiar species under the seismic action. The results show that some peculiar species abundance generally appeared to vary in similar manners during the pre- and post-earthquake periods， hydrogeochemical parameters were insensitive to the earthquakes, bacterial community structures were stable and earthquakes did not significantly affect the dominant groups and their diversity. The abundance of peculiar species slightly increased in pre-earthquake times, the maximum value appeared within 1 to 12 days after the earthquakes, and then declined to a lower level. Besides, the variations were correlated to earthquake magnitude and epicenter distance. The results suggest that some bacterial species could sensitively respond to earthquakes.