Abstract: The degradation and utilization of the anionic surfactant LAS (Linear alkylbenzene sulfonate) by Aeromonas sp. D-4 were studied with flask shaking technigue. Results show that Aeromonas sp. D-4 cannot use LAS as sole carbon source directly, but it is able to utilize LAS through certain process during co-metabolism. LAS is toxic to D-4 and its toxicity appears to be higher when higher concentration of LAS is present in the medium. The maximum removal rete of LAS is negatively correlated with the initial concentration of LAS. When the initial concentration of LAS ranges 40-120 mg/l, comparatively higher removal rates can be obtained. And, in the experiment, over 80% of the pollutant was removed when an initial concentration of LAS was about 40 mg/1. Moreover, the removal rate (Max. 84. 97%) of pure culture of Aeromonas sp. D-4 was higher then hat (Max. 78.57%) of mixed bacterial culture.