A strain PA-18 was isolated from the active sludge of p-phthalic acid (PTA) wastewater treatment in Yangtze Petrochemical Company.The 16SrDNA fragment was amplified from strain PA-18 by PCR，and the 16SrDNA sequence analysis indicated that strain PA-18 shared 99% 16SrDNA sequence homology with Pseudomonas sp..In the phylogenetic framework of bacterial classification，PA-18 belongs to Pseudomonas sp..Under the condition of temperature 37℃，pH 7.0 and OD660 nm2.0，the PTA decomposition rate of this bacterial strain was beyond 95% after 24 h.Meanwhile，this strain also could treat PTA wastewater with CODCr removal of 85%.p-Phthalic acid was degraded by the strain PA-18 through the intermediate formation of protocatechuic acid in the aerobic state.