The　influence　of　Fe2O3　impurity　on　the　crystalline　structure　of　cordierite　synthesized　from　waste　aluminum　slag　is　discussed.　XRD　and　SEM　techniques　were　employed　to　characterize　the　crystalline　structure　and　microstructure　of　each　specimen.　Philips　X＇pert　plus　software　was　used　to　determine　the　lattice　parameters　of　each　specimen.　The　results　show　that　the　Fe2O3　content　of　0.8　similar　to　1.6wt%　is　beneficial　to　the　formation　of　cordierite,　with　the　cordierite　amount　reaching　90wt%.　So　0.8　similar　to　1.6wt%　is　considered　as　the　allowable　Fe2O3　content　in　the　specimens　and　0.8wt%　is　determined　to　be　the　best　after　overall　analysis.　Plus　software　analysis　shows　that　the　cordierite　in　each　specimen　has　the　same　symmetrical　hexagonal　structure　as　the　single　crystal,　and　the　lattice　parameters　as　well　as　the　lattice　dimensions　change　slightly.