CrO3/NaY and CrO3/NaM zeolite systems have beed studied by X-ray diffraction (XRD). CrO3/NaY(or CrO3/NaM) samples with various amounts of CrO3 were prepared by mixing CrO3 and NaY(or NaM) in dry atmosphere, and by baking at 170 ℃ for 24 hours. The results showed that CrO3 could disperse spontaneously onto NaY, NaM zeolites as a non-crystalline layer during baking. The framework of NaY and NaM zeolites was destroyed by the dispersed CrO3 because of the strong surface interaction. The crystallinity of NaY(or NaM) decreased with the increase of CrO3 loading.