The　influence　of　K20　impurity　on　the　crystalline　structure　of　cordierite　synthesized　from　waste　aluminum　sludge　was　discussed.　XRD　and　SEM　techniques　were　used　to　characterize　the　crystalline　phases　and　microstructures　of　each　specimen.　Philips　X＇　pert　software　was　used　to　determine　the　lattice　parameters　of　each　specimen.　The　results　suggest　that　0.23-1.lwt%　content　of　K2O　is　beneficial　to　the　forming　of　the　cordierite,　but　the　continuous　increasing　of　K2O　will　reduce　the　cordierite　content,　therefore　1.lwt%　of　K2O　is　the　best　content.　Plus　software　analyses　show　that　cordierite　has　the　same　structure　as　single　crystal　in　each　specimen　and　the　lattice　parameters　change　slightly.