Legionella pneumophila has been known as an important pathogen causing Legionnaires Disease (LD), responsible for more than 80 per cent of clinical LD cases and majority of the LD outbreaks. In order to detect the existence of Legionella pneumophila strains in water samples, we have developed a ploymerase chain reaction method, using two primers synthesized according to the reported Legionella pneumophila mip gene nucleotide sequence. This method was proved to be highly sensitive (18 cfu/ml) and specific. Two water samples were detected positive. This newly developed method provided a quick, accurate way not only to detect Legionella pneumophila in the diagnosis of LD but also in the capture of suspected pathogen during epidemiologic investgation when LD outbreaks.