Abstract: Twe strains of bacteria which are able to grow on parathion and p-nitrophenol as sole carbon sources were isolated from the oxidation pond in YL region. The bacteria were indentified as Psuedomonas sp. CTP-01 and CTP-02 respectively. Parathion was rapidly degraded by Pseudomonas sp. CTP-01 to produce diethyl thiophosphate and p-nitrophenol, the latter being further metabolized. The enzymatic hydrolysis of parathion was investigated. Cellfree enzyme preparation of Psuedomonas sp. CTP-01 hydrolyzed parathion at maximum rate of 1×104n moles/rag Prot./min. The optimum temperature was 45—50℃. The activity was eompletly lost at 80℃. The optimum pH for the activity of cell free enzyme preparation is 7.0—7.5. Cu++ ion caused activation of the enzyme. In the presence of 10-3M Cu++ the activity increased about 20 time.