Atrazine (AT), a kind of herbicide for the pre and post-emergence control of annual and broad leaved weeds and perennial grasses, had been widely used in the world. However, the extensive use of atrazine had led to widespread environmental pollution. A bacterium strain SA1, which could degrade AT completely, was isolated from an atrazine-degrading consortium by long-time repeated alternative cultivation and plate striking. Combining cultural and physiobiochemical characteristics with 16S rDNA sequence analysis, SA1 was identified as Pseudomonas sp.. SAl could use atrazine as the sole carbon, nitrogen and energy sources for growth, and the main product of AT biodegradation was cyanuric acid. AT degrading activity of SA1 was not affected by the addition of nitrogen resources. However, cyanuric acid could be degraded quickly to an undetectable level when glucose was added. The optimal temperature and pH value for SAl growth was 37 degrees C and pH7, respectively. Atrazine could be degraded efficiently by the resting cells of SAl under the conditions of 10 degrees C - 40 degrees C or pH value 4-11, and SA1 had a wide range of temperature and pH value for AT degradation when compared with ADP. atzABCD and conserved sequence of tnpA gene of IS1071 could be amplified from SA1, and these genes could be lost during subculture.