Large water-level-fluctuation zone was formed after the impoundment of the Three Gorges Reservoir.The microbial diversity of this area could be greatly influenced by the water level fluctuation.The enumeration and BIOLOG-ECO methods were used to assess the microbial diversity in the water-level-fluctuation zone.Results showed that the quantity of cultured microorganisms was highly dependent on the position.The quantity of cultured microorganisms changed over time.The data of BIOLOG demonstrated clearly that the diversity index of most soil samples did not changed significantly.The soil microbes from different soil samples utilized different carbon sources,and their ability to utilize certain carbon sources increased with time.