Abstract: The microbial degrading characteristic of dimethylphthalate (DMP) was investigated by a strain FS1 isolated from the activated sludge at a petrochemical factory. The optimum pH of the stain FS1 microbial degradation for DMP is 6.58.0 and the optimum temperature is 2035 . The degradation of DMP can be described by the first-order reaction model. The experimental results demonstrated that the strain FS1 has strong ability of degrading DMP.