The full\|length cDNA of mosquito esterase B1 had been isolated,and subcloned into pBV220.The recombinant vector pBV220B1 was constructed and transformed into E.coli DH5α.A 60 kD protein was induced by 42℃ and its expression was temperature\|dependent.After 6h induction,the target protein occupied 50% of the total protein.The expressed product existed in both inclusion body and soluble proteins in the cells.The amount of the soluble detoxifying enzyme increased along with the induction time.The data of detoxifying experiments indicated that the detoxifying enzyme in expression strain of E.coli can detoxified toxicity of organophosphate insecticides,it showed a clear detoxifying affect on hens poisoned by organophosphate insecticides.