The mechanizm of PAH formation and the existing form are decribed and an effieient liquid phase chromotographic method for detection of naphthalene,anthracene and pyrene,3 typical PAH existed in air,has been established.In order to understand the emission of PAH in power plant,high content PAH coal powder samples of 125 MW unit were selected and analysed.The result showed that the PAH emission is very low and unharmful to the enviroment.