Abstract: A bacterium strain HS-D38 capable of degrading methyl parathion(MP) was isolated from the soil in which organophosphorus pesticides had been used for a long period.This strain can use MP as the sole carbon and nitrogen sources.It was used to degrade MP and it was indicated that the strain could also degrade p-nitrophenol(PNP) produced in the degradation of MP.The strain of HSD38 can use phenylamine as the sole nitrogen source and hydroquinone as the sole carbon source.The plasmid-cured strain could not degrade MP and PNP,which indicated that the enzyme of degradation was involved in plasmid.The characteristics of HS-D38 strain were investigated including cell morphology,biochemical characteristics,16S rDNA amplification,sequencing,and BLAST analysis.The phylogenetic tree of HS-D38 was constructed.All these results indicated that HS-D38 belonged to Pseudomonas aeruginosa.