Organophosphorus compounds (OP compounds) are toxic, because they can inhibit the acetylcholine esterase in central nervous system of human and animals. OP compounds are extensively used for insecticides control. Water, soil and agricultural products have been contaminated seriously by OP compounds in some regions. It is urgent to find effective methods to remove OP compounds contamination. In this study, an organophosphorus-degrading bacterium (strain YF-5) was isolated from sludge. Based on the results of phenotypic features and phylogenetic similarity of 16S rRNA gene sequences, strain YF-5 was identified as Pseudomonas sp. In liquid culture, 100 mg l^-1 methyl parathion and chlorpyrifos were decomposed completely by strain YF-5 (10⁶ cells mL^-1) within 8 h and 20 h, respectively. The methyl parathion degrading (mpd) gene was cloned from strain YF-5. Result of sequence BLAST indicated that this gene has 99% similarity to mpd of Plesiomonas sp. M6.