Pyrroloquinoline Quinone(PQQ)is a novel prosthetic group and differs from nicotinamid nucleotides,flavin nucleotides ever studied.In the recent decades,PQQ has been studied in Holland,Japan etc,but it was started studying lately in our country.The discovery, isolation,purification, assay,properities and functions of PQQ are introduced.It is beneficial for further studies of it existence,reaction mechanism, biological properities ,physiological functions and application of PQQ .Studying the new prosthetic group has important significents in theory and practice for the development of enzyme sciences.